#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define rep3(i, l, n) for (int i = l; i < n; ++i)
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define out(a) cout << a << endl
#define SZ(v) (int)v.size()
#define inf (int)(1e9+7)
int main() {
    string s; cin >> s;
    if (s[0] != '1') {
        out(-1);
        return 0;
    }
    rep3(i, 1, SZ(s)) if (s[i] - '0' != 3) {
        out(-1);
        return 0;
    }
    out(SZ(s) - 1);
    
    
}