#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

int main() {
    string s;
    cin >> s;

    int n = s.size() - 1;

    if (s[0] != '1') n = -1;
    for (int i = 1; i <= n; i++) {
        if (s[i] != '3') n = -1;
    }
    if (n == 0) n = -1;

    cout << n << endl;

    return 0;
}