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

int main(){
    char c;
    cin >> c;
    if(c != '1')return 0 & puts("-1");
    long i = 1;
    cin >> c;
    while(c == '3')++i;
    if(c != -1)return 0 & puts("-1");
    cout << i << endl;
    return 0;
}