Increasing Array

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

int main()
{
	unsigned int i, n, edits=0, last_num=1, num;
	signed int diff;
	cin >> n;

	for(i=0;i<n;i++) {
        cin >> num;
        diff = last_num - num;
        if (diff > 0) {
            edits += diff;
        } else {
            last_num = num;
        }
	}
	cout << edits;
    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: ACCEPTED