#include <bits/stdc++.h>
using namespace std;
using lint = long long;
template<class T = int> using V = vector<T>;
template<class T = int> using VV = V< V<T> >;


int main() {
  cin.tie(nullptr); ios::sync_with_stdio(false);
  string s; cin >> s;
  int n = s.size();
  int res;
  if (s[0] != '1') res = -1;
  else {
    res = n - 1;
    for (int i = 1; i < n; ++i) if (s[i] != '3') res = -1;
  }
  cout << res << '\n';
}