include [HTML_REMOVED]

using namespace std;
int solve(int n, int m){Preferences
int i, sum;
if (m == 1) return 1;
sum = 0;
for (i = 1; i < n; i++)
sum += solve(i, m - 1);
return sum;
}
int main(){
int n, m;
cin>>n>>m;
cout<<solve(n, m)<<endl;
return 0;
}
输入：7 4
输出 ：20