#include <bits/stdc++.h>
using namespace std;
#define MOD (ll)(1e9+7)
typedef long long int ll;
//each row <=2
//each col <=2
//cant have triangle
inline void mod(ll &x){
if(x>=MOD)x-=MOD;
}
ll dp[2][301][301];
ll C[3001][3001];
int main()
{
dp[0][0][0] = 1;
for(int i=0;i<=3000;i++){
for(int j=C[i][0] = 1;j<=i;j++){
C[i][j] = C[i-1][j-1] + C[i-1][j];
mod(C[i][j]);
}
}
int h,w;
cin>>h>>w;
for(int i=0;i<h;i++){
for(int j=0;j<=w;j++){ //bad col
for(int k=0;k<=w;k++){ //occu col
if(!dp[0][j][k])continue;
int emp = w-k-j;
if(k){//place a single on occu and increase bad col by 1
dp[1][j+1][k-1] += dp[0][j][k] * k %MOD;
mod(dp[1][j+1][k-1]);
}
if(emp){
//place a single on emp but its not faced south then increase bad col by 1
dp[1][j+1][k] += dp[0][j][k] * 3 * emp%MOD;
mod(dp[1][j+1][k]);
//place a single on emp but its faced south then increase occu col by 1
dp[1][j][k+1] += dp[0][j][k] * emp%MOD;
mod(dp[1][j][k+1]);
}
if(emp>=2){//place two on emp and increase bad col by 2
dp[1][j+2][k] += dp[0][j][k] * 1LL * C[emp][2]%MOD;
dp[1][j+2][k]%=MOD;
}
dp[1][j][k]+=dp[0][j][k];
mod(dp[1][j][k]);//do nothing
}
}
for(int j=0;j<=w;j++){
for(int k=0;k<=w;k++){
dp[0][j][k] = dp[1][j][k];
dp[1][j][k] = 0;
}
}
}
ll ans = 0;
for(int i=0;i<=w;i++){
for(int j=0;j<=w;j++){
//cout<<i<<" "<<j<<" "<<dp[0][i][j]<<'\n';
ans+=dp[0][i][j];
mod(ans);
}
}
ans+=MOD-1;
mod(ans);
cout<<ans;
}
