Pile

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main() {
    //cout << "foo" << endl;
    cin.sync_with_stdio(false);
    ll n;
    cin >> n;
    stack<int> blox;
    bool good = true;
    //cout << "bar" << endl;
    for (ll i = 0; i < n; i++) {
        ll cur;
        cin >> cur;
        //cout << "reading " << cur << endl;
        //if (!blox.empty()) cout << "stack top " << blox.top() << endl;
        if (blox.empty() || blox.top() < cur) {
            //cout << "derp" << endl;
            blox.push(cur-1);
        } else if (blox.top() == cur) {
            //cout << "dorp" << endl;
            blox.pop();
        } else {
            good = false;
            //cout << "darp" << endl;
            break;
        }
        //cout << "foob" << endl;
    }

    if (good) {
            cout << "Not a proof" << endl;
    } else {
            cout << "Cheater" << endl;
    }

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: ACCEPTED

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: ACCEPTED

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: ACCEPTED

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: ACCEPTED

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: ACCEPTED

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: ACCEPTED

Test 18

Verdict: WRONG ANSWER

Test 19

Verdict: ACCEPTED

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: ACCEPTED

Test 22

Verdict: WRONG ANSWER

Test 23

Verdict: ACCEPTED

Test 24

Verdict: WRONG ANSWER

Test 25

Verdict: ACCEPTED

Test 26

Verdict: WRONG ANSWER

Test 27

Verdict: ACCEPTED

Test 28

Verdict: WRONG ANSWER

Test 29

Verdict: ACCEPTED

Test 30

Verdict: WRONG ANSWER