#include <iostream>
using namespace std;

void combination(const char *str, int start, int end, int m, char *cmb, int m_exist){
if(m==0){
    cout<<"{";
    for(int i=m_exist-1; i>0; i--)
      cout<<cmb[i]<<", ";
    cout<<cmb[0]<<"}"<<endl;

    return;
  }

  for(int i=start; i<end; i++){
    cmb[m-1]=str[i];
    combination(str,i+1,end,m-1,cmb,m_exist);
  }

}
int main() {
string str("12345");

  int N=str.size();
  int M=2; //change M whatever you want

  char *cmb=new char[M];

  combination(str.c_str(), 0, N, M, cmb, M);

  delete [] cmb;

  return 0;
}