#include <iostream> #include <bits/stdc++.h> using namespace std;//集合划分问题 int hua(int n, int m) { if(m==1||n==m) return 1; else return hua(n-1,m-1)+m*hua(n-1,m); } int main() { // ifstream fin("stir10.in",ios::in); // ofstream fout("answer10.txt"); int n,m; cin>>n>>m; int count1; count1=hua(n,m); cout << count1; // fout.close(); // fin.close(); return 0; }