#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;


int main(){
  string N;
  cin >> N;

  if(N[0] != '1' || N.size() == 1){
    cout << -1 << endl;
    return 0;
  }else{
    REP(i,1,N.size()){
      if(N[i] != '3'){
        cout << -1 << endl;
        return 0;
      }
    }
    cout << N.size()-1 << endl;
  }
  
  return 0;
}