#include <iostream>
using namespace std;

int main() {
    int a[20];
    for (int i = 0; i < 20; i++) {
        cin >> a[i];
    }
    int min = 21; 
    for (int i = 0; i < 20; i++) {
        if (a[i] == 1) { 
            for (int j = i + 1; j < 20; j++) {
                if (a[j] == 0) { 
                    int d = j - i - 1;
                    if (d < min) {
                        min = d;
                    }
                    break; 
                }
            }
        }
    }

    if (min == 21) {
        cout << -1 << endl;
    } else {
        cout << min << endl;
    }

    return 0;
}