#include <bits/stdc++.h>
// #pragma GCC optimize ("Ofast,unroll-loops")
// #pragma GCC target ("avx2")
using namespace std;
typedef long long ll;
typedef pair<int, int> pp;
#define per(i,r,l) for(int i = (r); i >= (l); i--)
#define rep(i,l,r) for(int i = (l); i < (r); i++)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define pb push_back
#define ss second
#define ff first
void err(istringstream *iss){}template<typename T,typename ...Args> void err(istringstream *iss,const T &_val, const Args&...args){string _name;*iss>>_name;if(_name.back()==',')_name.pop_back();cerr<<_name<<" = "<<_val<<", ",err(iss,args...);}
void IOS(){
cin.tie(0) -> sync_with_stdio(0);
// #ifndef ONLINE_JUDGE
// #define er(args ...) cerr << __LINE__ << ": ", err(new istringstream(string(#args)), args), cerr << endl
// freopen("inp.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
// #else
// #define er(args ...) 0
// #endif
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll mod = 1e9 + 7, maxn = 3e3 + 5, lg = 22, inf = ll(1e9) + 5;
ll pw(ll a,ll b,ll md=mod){if(!b)return 1;ll k=pw(a,b>>1ll,md);return k*k%md*(b&1ll?a:1)%md;}
ll f[maxn][maxn];
ll C[maxn][maxn], G[maxn];
int main(){ IOS();
int n, m; cin >> n >> m;
rep(i,0,n+1){
rep(j,0,m+1){
f[i][j] = 1;
if(j && i) f[i][j] = (f[i][j-1] + 4ll*i*f[i-1][j-1])%mod;
}
}
rep(i,0,maxn){
C[i][0] = 1;
rep(j,1,i+1) C[i][j] = (C[i-1][j] + C[i-1][j-1])%mod;
}
G[0] = 1;
rep(i,1,maxn){
G[i] = 1ll*G[i-1]*i%mod*(2*i-1)%mod;
}
ll ans = mod - 1;
rep(a,0,n+1){
rep(b,0,m+1){
if(2*a + b <= n && 2*b + a <= m){
ans += f[n - 2*a - b][m - 2*b - a]*C[m][a]%mod*C[n][2*a]%mod*G[a]%mod*C[n-2*a][b]%mod*C[m-a][2*b]%mod*G[b]%mod;
ans %= mod;
}
}
}
cout << ans << '\n';
return 0-0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
27 ms |
46680 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
27 ms |
46680 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
27 ms |
46680 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |