#include <bits/stdc++.h>

using namespace std;

int main(){
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);

    string s;
    cin >> s;

    int sum = 0;
    for (char c : s){
        sum += (int)c - 48;
    }

    int d = sum % 3;

    int res = 0;
    if (d == 0){
        cout << 0;
    }
    else if (d == 1){
        if (s.length() == 1){
            cout << -1;
            return 0;
        }
        bool is_found = false;
        for (int i=0; i<s.length(); i++){
            int t = (int)s[i] - 48;
            if (t % 3 == 1){
                res++;
                is_found = true;
                break;
            }
        }

        if (!is_found){
            int t_2 = 0;
            for (int i=0; i<s.length(); i++){
                int t = (int)s[i] - 48;
                if (t % 3 == 2){
                    t_2++;
                }
            }

            if (t_2 == 2){
                if (s.length() == 2){
                    cout << -1;
                    return 0;
                }
                else{
                    cout << 2;
                    return 0;
                }
            }
            else{
                cout << -1;
                return 0;
            }
        }
        else{
            cout << res;
        }
    }
    else{
        if (s.length() == 1){
            cout << -1;
            return 0;
        }
        bool is_found = false;
        for (int i=0; i<s.length(); i++){
            int t = (int)s[i] - 48;
            if (t % 3 == 2){
                res++;
                is_found = true;
                break;
            }
        }

        if (!is_found){
            int t_1 = 0;
            for (int i=0; i<s.length(); i++){
                int t = (int)s[i] - 48;
                if (t % 3 == 1){
                    t_1++;
                }
            }

            if (t_1 == 2){
                if (s.length() == 2){
                    cout << -1;
                    return 0;
                }
                else{
                    cout << 2;
                    return 0;
                }
            }
            else{
                cout << -1;
                return 0;
            }
        }
        else{
            cout << res;
        }
    }
}