Hi, I was solving this problem a few minutes ago, and the following problem is a subproblem of this one.

Given integer &n&, and array &a& consisting of &n — 1& integers, all of them are equal to some value &b&. Later, some integer &c& is chosen, such that &c != b&, and beign inserted to the array &a& at random position. By given &n& and &a& find &c&.

#include <bits/stdc++.h>

using namespace std;

int a[100001] = {0};

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    for(int i = 0; i < n; i++)
        cin >> a[i];
    
    return 0;
}