#include <iostream>
#include <cstdlib>
#include <vector>
#include <algorithm>
int main()
{
    std::string s;
    std::cin >> s;
    int cnt = -1;
    for(auto i = s.begin(); i != s.end(); i++){
        char c = *i;
        if(cnt == -1){
            if(c != '1'){
                std::cout << -1 << std::endl;
                return 0;
            }
        } else {
            if(c != '3'){
                std::cout << -1 << std::endl;
                return 0;
            }
        }
        cnt++;
    }
    std::cout << cnt << std::endl;
    return 0;
}