#include <bits/stdc++.h>
#define rep(i, ss, ee) for (int i = ss; i < ee; ++i)
using namespace std;

void solve() {
  string s;
  cin >> s;
  smatch m;
  regex_search(s, m, regex("(^13*)"));
  cout << ((s.size() > 1 && s.size() == m.length()) ? m.length() - 1 : -1)
       << endl;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
  getchar();
}