#include <iostream>
using namespace std;
long long comb(int n, int m) {
if (m == 0 || m == n) {
return 1;
}
long long dp[n + 1][n + 1];
for (int i = 0; i <= n; i++) {
dp[i][0] = 1;
dp[i][i] = 1;
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j < i; j++) {
dp[i][j] = (dp[i-1][j] + dp[i-1][j-1]) % 1000000007;
}
}
return dp[n][m];
}
int main() {
int n, m;
cin >> n >> m;
cout << comb(n, m) << endl;
return 0;
}
