#include<bits/stdc++.h>
using namespace std;
typedef int ll;
typedef long double ld;
typedef pair<ll,ll> pll;
const ll N=3e3+5;
const ll M=1e4+5;
const ll MOD=1e9+7;
const ld pi=acos(-1);
const ll MOD2=998244353;
const ll INF=(1LL<<60);
#define REP(i,n) for(ll i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define lwb lower_bound
#define SZ(a) (ll)a.size()
ll n,m,dp[N][N];
ll C(ll k){
if(k<2)return 0;
return (k*(k-1)%MOD)*r%MOD;
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n>>m;
REP(i,n+1)dp[i][0]=1;REP(i,m+1)dp[0][i]=1;
REP1(i,n){
REP1(j,m){
dp[i][j]+=dp[i-1][j];
dp[i][j]+=dp[i-1][j-1]*j*4;
dp[i][j]+=dp[i-1][j-2]*(C(j));
dp[i][j]+=dp[i-2][j-1]*(i-1)*j;
dp[i][j]%=MOD;
}
}
cout<<dp[n][m]<<"\n";
return 0;
}
Compilation message
tents.cpp:11:18: warning: overflow in implicit constant conversion [-Woverflow]
const ll INF=(1LL<<60);
~~~~^~~~~
tents.cpp: In function 'll C(ll)':
tents.cpp:25:23: error: 'r' was not declared in this scope
return (k*(k-1)%MOD)*r%MOD;
^
