题解

#include<bits/stdc++.h>
using namespace std;
long long a[1003][1003];
int main(){
    a[0][1] = 1;
    a[1][2] = 1;
    int n,m;
    cin >> n >> m;
    for(int i = 1;i <= m + 1;i ++){
        for(int j = 2;j <= n + 2;j ++){
            a[i][j] = (a[i - 1][j - 1] + a[i][j - 1]) % 1000000007;
        }
    }
    cout << a[m + 1][n + 2];
    return 0;
}