#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  string n;
  cin >> n;
  bool ok = (n[0] == '1');
  if (n == "1") ok = false;
  rep(i, n.size() - 1) if (n[i + 1] != '3') ok = false;
  cout << (ok ? (int) n.size() - 1 : -1) << endl;
  return 0;
}