#include "bits/stdc++.h"

#define REP(i,n) for(ll i=0;i<ll(n);++i)
#define RREP(i,n) for(ll i=ll(n)-1;i>=0;--i)
#define FOR(i,m,n) for(ll i=m;i<ll(n);++i)
#define RFOR(i,m,n) for(ll i=ll(n)-1;i>=ll(m);--i)
#define ALL(v) (v).begin(),(v).end()
#define UNIQUE(v) v.erase(unique(ALL(v)),v.end());
#define INF 1000000001ll
#define MOD 1000000007ll
#define EPS 1e-9

constexpr int dx[8] = { 1,1,0,-1,-1,-1,0,1 };
constexpr int dy[8] = { 0,1,1,1,0,-1,-1,-1 };


using namespace std;

using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using vvi = vector<vi>;
using vvl = vector<vl>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

template <class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
template <class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }

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

}