Submission #1287734

#TimeUsernameProblemLanguageResultExecution timeMemory
1287734muhammad-ahmadLine Town (CCO23_day1problem3)C++20
0 / 25
1 ms1344 KiB
#include <bits/stdc++.h>
using namespace std;

#define int long long
#define endl '\n'

void solve(){
	int n; cin >> n;
	vector<int> a(n);
	for (auto &i : a) cin >> i;
	vector<int> idx;
	for (int i = 0; i < n; i++){
		if (a[i] == -1) idx.push_back(i);
	}
	
	n = idx.size();
	
	if (n % 2) cout << -1 << endl;
	else {
		for (int i = 0; i < n; i++){
			if (idx[i + 1] - idx[i] > 1){
				cout << -1 << endl;
				return;
			}
		}
		
		cout << n / 2 << endl;
		
	} 
	
	
}

signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int tc = 1;
	// cin >> tc;
	while (tc--){
		solve();
	}
}
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