Increasing Array

#include <iostream>
using namespace std;

int main(int argc, char *argv[]) {
    unsigned long n, t=0;
    cin >> n;
    unsigned long p;
    cin >> p;
    n--;
    while (n--) {
        unsigned long q;
        cin >> q;
        if (q < p) t += p-q;
        else p = q;
    }
    cout << t << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED