M-th to Last Element

#include <cmath>
#include <cstdio>
#include <deque>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    long long m;
    deque<int> A;
    int n;
    scanf("%lld",&m);
    while(scanf("%d", &n) != EOF) {
        A.push_back(n);
        if(A.size() > m) A.pop_front();
    }
    if(A.size() == m) cout<<A[0];
    else cout<<"NIL";
    return 0;
}