#include "bits/stdc++.h"
#define LF '\n'
#define ALL(x) x.begin(), x.end()
#define LEN(x) (int)x.size()
#define iostreamBooster() do{ cin.tie(nullptr); ios_base::sync_with_stdio(false); }while(0)
using namespace std;
typedef int64_t i64;
typedef pair<int,int> pii;
template<class A, class B>inline bool chmax(A &a, const B &b){return b>a ? a=b,1 : 0;}
template<class A, class B>inline bool chmin(A &a, const B &b){return b<a ? a=b,1 : 0;}
constexpr int INF = 0x3f3f3f3f;
template<class Itr>void dump(Itr begin, Itr end) {
  for(;begin != end; ++begin) clog << ' ' << *begin;
  clog << LF;
}

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

  if (s[0] != '1' || !all_of(s.begin()+1, s.end(), [](const auto &c){
        return c == '3'; })
  ) {
    cout << -1 << endl;
  } else {
    cout << s.length() - 1 << endl;
  }



  return 0;
}