【加急】求条，90分

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

int main() {
	int n;
	cin >> n;
	vector<int> a(n + 1);
		for (int i = 1; i <= n; i++)
			cin >> a[i];
		int ans = 0;
		int l = 0, r = 0;
		bool flag = false;
		for (int i = 1; i <= n; i++) {
			if (flag == false && a[i] == 1) {
				flag = true;
				l = i;
				r = i;
			}
			if (flag == true && a[i] == 1) {
				r = i;
			}
		}
		ans = r - l + 1;
		printf("%d\n", ans);
	return 0;
}