#include <iostream>
#include <vector>
 
using namespace std;
 
 //This generates all nCr sequences
void display(const std::vector<int> & v, 
             std::vector<int>& comb, 
             int offset, int k) {
    if (k == 0) {
        std::cout<<"{";
        for(auto &x:comb)
            std::cout<<x<<" ";
         std::cout<<"\b}"<<std::endl;
    return;
    }
    for (int i = offset; i <= v.size() - k; ++i) {
        comb.push_back(v[i]);
        display(v,comb,i+1, k-1);
        comb.pop_back();
    }
}
     
int main() {
    int n = 4;
    
     std::vector<int> v,comb;
    for (int i = 0; i < n; ++i) 
     v.push_back(i+1); 

    for (int i = 1; i <= n; ++i) 
        display(v,comb,0, i);
 
return 0;
}