...

#include<iostream>
using namespace std;
int a[1005][1005];
int main(){
int n , m;
cin >> n >> m;
for(int i = 1;i <= m;i++) a[1][i] = 1;
for(int i = 1;i <= n;i++) a[i][1] = 1;
for(int i = 2;i <= n;i++){
for(int j = 2;j <= m;j++){
a[i][j] = a[i-1][j] + a[i][j-1];
}
}
cout << a[n][m];
return 0;
}