#include<algorithm>
#include<iostream>
#include<stdio.h>
#include<string>
#include<vector>
#include <cmath>
#include <algorithm>
#include <functional>

using namespace std;
typedef long long ll;

int gcd(int m,int n)
{
	// 引数に０がある場合は０を返す
	if ( ( 0 == m ) || ( 0 == n ) )
		return 0;
	
	// ユークリッドの方法
	while( m != n )
	{
		if ( m > n ) m = m - n;
		else         n = n - m;
	}
	return m;
}//gcd



int main(){
    // input
    ll N;
    cin >>N;
    
    //vector<int> v(N);
    //std::sort(g.begin(),g.end());

    ll ans = 0;
    ll out = -1;
    int flag = 1;


    while(flag != 0){
        N = N-3;
        
        if(N % 10 == 0){
            N = N /10;
            ans++;
        }else{
            flag = 0;
            out = -1;
        }

        if( N==1){
            flag =0;
            out = ans;
        }

        if(N<=0){
            out = -1;
            flag = 0;
        }


    }
    cout << out << endl;


    return 0;
}