This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h>
 
using namespace std;
namespace std {
    // #include<Love>
    using ll=long long;
    using str=string;
    using int128=__int128_t;
    using ld=long double;
 
    typedef unsigned int ui;
    typedef unsigned long long ull;
 
    #define Love<3 HerLoveForMeJustaDream
}
 
#define Lovesper_ ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define pll pair<ll,ll>
#define mll map<ll,ll>
#define vll vector<ll>
#define pb push_back
#define all(c) c.begin(),c.end()
#define fi first
#define se second
#define debug cout<<"I Love You\n";
#define fu(i,a,b) for(ll i=a;i<=b;i++)
#define fd(i,a,b) for(int i=a;i>=b;i--)
#define fa(i,s) for(auto&i:s)
#define Bitc(x,i) (((x)>>(i))&1)
#define _log(_x) 63-__builtin_clzll(_x)
#define LoveTime chrono::steady_clock::now().time_since_epoch().count()
 
const pll dxy4[]={{-1,0},{0,-1},{0,1},{1,0}};
const pll dxy8[]={{-1,-1},{-1,0},{-1,1},{0,-1},{0,1},{1,-1},{1,0},{1,1}};
constexpr  ll Mod=1e9+7;
constexpr  ll mxn=1e6+7,mxm=3e3+7;
constexpr long long inf=(1ll<<31);
constexpr ll lnf=(1ll<<60);
 
struct __TS {
    ~__TS() {
        // cerr<<"Time elapsed: "<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
    }
}__ts;
 
mt19937 rng(LoveTime);
 
#define setup ((1<<3)-1>>1)
void OpenLove(const str&name){
 
    // I'm So Lonely. I am Trying To Get Out This Lonely With Her Love
 
    Lovesper_
    if(fopen((name+".inp").c_str(),"r")){
    // freopen((name+".test").c_str(),"r",stdin);
        freopen((name+".inp").c_str(),"r",stdin);
        freopen((name+".out").c_str(),"w",stdout);
    }
}
template<class X,class Y>bool maximize(X&x,const Y&y){X eps=1e-18;if(x+eps<y){x=y;return 1;}return 0;}
template<class X,class Y>bool minimize(X&x,const Y&y){X eps=1e-18;if(x>y+eps){x=y;return 1;}return 0;}
 
template <class Fun>class y_combinator_result {
    Fun fun_;
    public:
    template<class T>explicit y_combinator_result(T &&fun): fun_(std::forward<T>(fun)) {}
    template<class ...Args>decltype(auto) operator()(Args &&...args) {return fun_(std::ref(*this), std::forward<Args>(args)...);}
};
template<class Fun>decltype(auto) y_combinator(Fun &&fun) {return y_combinator_result<std::decay_t<Fun>>(std::forward<Fun>(fun));}
 
ostream&operator<<( std::ostream& dest, __int128_t value){
    ostream::sentry s(dest);__uint128_t tmp=value<0?-value:value;
    char buffer[128];char*d=end(buffer);
    do{d--;*d="0123456789"[tmp%10];tmp/=10;}while(tmp);
    if(value<0)d--,*d='-';ll len=end(buffer)-d;
    if(dest.rdbuf()->sputn(d,len)!=len)dest.setstate(ios_base::badbit);
    return dest;
}
 
struct custom_hash{
    size_t operator()(uint64_t x)const{
        static const uint64_t HashRand=LoveTime;
        x^=HashRand;return x^(x>>16);
}};
 
int64_t add(ll&a,ll b){a+=b;if(a>=Mod)a%=Mod;while(a<0)a+=Mod;return a;}
int64_t mul(ll&a,ll b){a=1ll*a*b%Mod;return a;}
int64_t mpow(ll a,ll b,ll mod){ll ans=1;for(;b;b>>=1,a=mul(a,a))if(b&1)ans=mul(ans,a);return ans;}
 
ll n,m,k,f[mxn],g[mxn];
vll graph[mxn];
void Lovesper(const ll&TestCase){
    cin>>n>>m>>k;
    fu(i,2,n){
        ll u,v;cin>>u>>v;
        graph[u].pb(v);
        graph[v].pb(u);
    }
    struct Love1{
        function<void()>DreamyLove=[&](){
            ll x,y;cin>>x>>y;
            auto dfs=y_combinator([&](auto&&dfs,ll u,ll p)->void {
                for(auto&v:graph[u]){
                    if(v==p)continue;
                    f[v]=f[u]+1;
                    dfs(v,u);
                }
            });
            dfs(x,0);
            ll len=f[y];
            ll a=mpow(k,len/2+(len&1),Mod);
            ll b=mpow((ll)(k-1),len/2,Mod);
            cout<<a*b%Mod;
        };
    };
    // (new Love1())->DreamyLove();
    if(m==1)(new Love1())->DreamyLove();
}
signed main(int argc, char const *argv[]){
    OpenLove("lovesper");
    int tt=1;
    // cin>>tt;
    for(ll i=1;i<=tt;i++){
        Lovesper(i);
        if(i<tt)cout<<'\n';
    }
    return false;
}
Compilation message (stderr)
Main.cpp:14:13: warning: ISO C++11 requires whitespace after the macro name
   14 |     #define Love<3 HerLoveForMeJustaDream
      |             ^~~~
Main.cpp: In function 'std::ostream& operator<<(std::ostream&, __int128)':
Main.cpp:75:5: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   75 |     if(value<0)d--,*d='-';ll len=end(buffer)-d;
      |     ^~
Main.cpp:75:27: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   75 |     if(value<0)d--,*d='-';ll len=end(buffer)-d;
      |                           ^~
Main.cpp: In function 'void OpenLove(const str&)':
Main.cpp:56:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |         freopen((name+".inp").c_str(),"r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:57:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |         freopen((name+".out").c_str(),"w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... |