indices of sorted array

#include <vector>
#include <utility>
#include <algorithm>
#include <iostream>

using namespace std;
int main()
{
    const int N = 4;
    int input[] = { 4, 3, 2, 1 };

    vector< pair< int , int > > vec(N);
    for(int i = 0; i < N; ++i) { vec[i] = make_pair(input[i], i); }
    sort(vec.begin(), vec.end());

    for(int i = 0; i < N; ++i) { cout << vec[i].second; }
    return 0;
}