#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvvl vector<vvl>
#define vvl vector<vector<ll>>
#define VV(a, b, c, d) vector<vector<d>>(a, vector<d>(b, c))
#define VVV(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define re(c, b) for(ll c=0;c<b;c++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

bool judge(string s){
  if(s[0]!='1') return false;
  for(int i=1;i<s.size();i++) if(s[i]!='3') return false;
  return true;
}

int main(int argc, char const *argv[]) {
  string s;std::cin >> s;
  ll ans = (judge(s)?s.size()-1:(ll)-1);
  std::cout << ans << '\n';
  return 0;
}