Key cutting

#include <iostream>
#include <vector>
using namespace std;
int main() {
	int n;
	cin>>n;
	int res=0;
	vector<int> st;
	while(n--) {
		int x;cin>>x;
		while(!st.empty() && x<st.back()) {
			st.pop_back();
			++res;
		}
		if (x==0) continue;
		if (st.empty() || x>st.back()) {
			st.push_back(x);
		}
	}
	cout<<res+st.size()<<'\n';
}

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

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED