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

void repeatedNumber(const vector<int> &arr) {
    int n = arr.size();
  
    int s = (n * (n + 1)) / 2;
    int ssq = (n * (n + 1) * (2 * n + 1)) / 6;
  
    int missing = 0, repeating = 0;
    
    for (int i = 0; i < arr.size(); i++) {
       s -= arr[i];
       ssq -= arr[i] * arr[i];
    }
    
    missing = (s + ssq / s) / 2;
    repeating = missing - s;
    
    cout << "Repeating : " << repeating << endl;
    cout << "Missing " << missing;
}

int main(void) {
    vector<int> arr = {4, 3, 6, 2, 1, 6, 7};
    repeatedNumber(arr);
    return 0;
}