#include <iostream>
using namespace std;

int main() {
    int B = 0;
    int TEMP_B = 0;

    for (int i = 0; i < 9; i++) {
        cin >> B;
        if (B - TEMP_B != 1) {
            cout << i + 1 << endl;
            return 0;
        }
        TEMP_B = B;
    }
    cout << 10 << endl;
    return 0;    
}