#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int main() {
  string N;
  cin >> N;
  if (N[0] != '1' || N.size() < 2) {
    cout << -1 << endl;
  } else {
    for (size_t i = 1; i < N.size(); i++) {
      if (N[i] != '3') {
        cout << -1 << endl;
        return 0;
      }
    }
    cout << N.size() - 1 << endl;
  }
  return 0;
}