#include <iostream>
#include <string>
using namespace std;
int main(void){
    string s;
    cin >> s;
    if(s[0] != '1' || s.length() == 1){
        cout << "-1" << endl;
        return 0;
    }
    for(long long i = 1; i < s.length(); i++){
        if(s[i] != '3'){
            cout << "-1" << endl;
            return 0;
        }
    }
    cout << s.length() - 1 << endl;
    return 0;
}