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>
#define ll long long
#define ld long double
#define ull unsigned long long
#define pb push_back
#define pll pair<ll, ll>
#define pii pair<ll, int>
#define fi first
#define se second
using namespace std;
const int N = 65;
const int M = 250;
const int mod = 1e9+7;
const ll base = 75;
const ll inf = 1e16;
int n, lab[N], tong, d[N], t, c[N], h[N], k, P[N][8], in[N], out[N], ntime, cnt;
int ans, m, a[N], b[N];
vector<int> adj[N];
vector<pll> vi;
string s;
bool vis[N];
struct edge
{
int x, y, z;
}e[N];
void add(int& x, int y)
{
x += y;
if(x >= mod)x -= mod;
}
void dfs(int u, int p = 0)
{
in[u] = ++ntime;
P[ntime][0] = u;
for(int v: adj[u])
{
if(v == p)continue;
h[v] = h[u]+1;
dfs(v, u);
out[u] = ++ntime;
P[ntime][0] = u;
}
}
int get(int l, int r)
{
if(l > r)swap(l, r);
int log = log2(r-l+1);
if(h[P[l][log]] < h[P[r-(1<<log)+1][log]])return P[l][log];
return P[r-(1<<log)+1][log];
}
void cal(int u, int p = 0)
{
bool ok = false;
for(int v: adj[u])
{
if(v == p)continue;
cal(v, u);
c[u] += c[v];
ok |= (c[v] > 0);
}
if(c[u] == 0)
{
if(u > 1)++tong;
if(ok)++tong;
}
}
void sol()
{
cin >> n >> m >> k;
for(int i = 1; i < n; i ++)
{
int x, y;
cin >> x >> y;
adj[x].pb(y);
adj[y].pb(x);
}
d[0] = 1;
for(int i = 1; i < n; i ++)d[i] = 1ll * d[i-1] * k % mod;
dfs(1);
for(int j = 1; j < 8; j ++)
{
for(int i = 1; i+(1<<j)-1 <= ntime; i ++)
{
if(h[P[i][j-1]] < h[P[i+(1<<(j-1))][j-1]])P[i][j] = P[i][j-1];
else P[i][j] = P[i+(1<<(j-1))][j-1];
}
}
for(int i = 0; i < m; i ++)
{
cin >> e[i].x >> e[i].y;
e[i].z = get(in[e[i].x], in[e[i].y]);
}
for(int mask = 0; mask < (1<<m); mask ++)
{
fill_n(c, n+1, 0);
for(int i = 0; i < m; i ++)
{
if(mask >> i & 1)
{
++c[e[i].x];
++c[e[i].y];
c[e[i].z] -= 2;
}
}
tong = 0;
cal(1);
//cout << mask <<" "<< __builtin_popcount(mask) <<" "<<tong << '\n';
if((__builtin_popcount(mask))&1)add(ans, mod-d[tong]);
else add(ans, d[tong]);
}
cout << ans;
}
int main()
{
cin.tie(0);
cout.tie(0);
ios_base::sync_with_stdio(0);
#define task "test"
if(fopen(task".inp", "r"))
{
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
int test = 1;
//cin >> test;
while(test -- > 0)sol();
return 0;
}
/*
1234
21
*/
Compilation message (stderr)
Main.cpp: In function 'int main()':
Main.cpp:121:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
121 | freopen(task".inp", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:122:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
122 | freopen(task".out", "w", stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
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