#include <bits/stdc++.h>

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = std::int64_t;
using P = std::tuple<int,int>;

std::string N;

int solve(){
    unless(N[0] == '1'){
        return -1;
    }

    unless(std::all_of(N.begin() + 1, N.end(), [](char c){return c == '3';})){
        return -1;
    }
    
    if(N.size() <= 1){
        return -1;
    }

    return N.size() - 1;
}

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    std::cin >> N;

    int ans = solve();
    std::cout << ans << std::endl;
}