stirling

#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n, k;
    cin >> n >> k;

    vector<vector<int>> stir(n + 1, vector<int>(k + 1));
    stir[0][0] = 1;

    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= min(i, k); j++)
            stir[i][j] = stir[i - 1][j - 1] + j * stir[i - 1][j];
    }

    cout << stir[n][k] << '\n';
    return 0;
}