#include <bits/stdc++.h>
using namespace std;
#define chmax(x, y) x = max(x, y)
int main(){
    string s;
    cin >> s;
    int n = s.length();
    int ans = -1;
    if(s[0] != '1'){
        cout << ans << endl;
        return 0;
    }
    for(int i = 1; i < n; ++i){
        if(s[i] != '3'){
            cout << ans << endl;
            return 0;
        }
    }
    ans = n - 1;
    cout << ans << endl;
}