#include <bits/stdc++.h>
using namespace std;
using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<long>;
using vs = vector<string>;
using vvi = vector<vector<int>>;
using vvb = vector<vector<bool>>;
using vvc = vector<vector<char>>;
using vvl = vector<vector<long>>;
using pii = pair<int, int>;
using pil = pair<int, long>;
using pll = pair<long, long>;
#define fix20 cout << fixed << setprecision(20)
#define YES cout << "Yes" << endl
#define NO cout << "No" << endl
#define rep(i,n) for(long i=0; i<(long)(n);i++)
#define REP(i,s,t) for(long i=s; i<t; i++)
#define RNG(i,s,t,u) for(long i=s; i<t; i+=u)
#define MOD 1000000007
#define all(vec) vec.begin(), vec.end()
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

int main(){
  string s;
  cin >> s;
  int sum = 0;
  vi cnt(3,0);
  rep(i,s.size()){
    int num = s.at(i) - '0';
    sum += num;
    cnt.at(num % 3)++;
  }

  if(sum % 3 == 0){
    
    cout << 0 << endl;
    return 0;
  }
  if(s.size() == 1){
    cout << -1 << endl;
    return 0;
  }else if(s.size() == 2){
    if(cnt.at(0) == 0){
      cout << -1 << endl;
    }else{
      cout << 1 << endl;
    }
    return 0;
  }else{
    int a = cnt.at(1);
    int b = cnt.at(2);
    int mini = 10000;
    for(int i=a;i>=0;i-=3){
      for(int j=b;j>=0;j-=3){
        //cout << i << j << endl;
        chmin(mini,abs(i-j));
      }
    }
    cout << mini << endl;
  }

}

 //                                                  '-.-'
   //                                         ()      __.'.__
   //                                      .-:--:-.  |_______|
   //                               ()      \____/    \=====/
   //                               /\      {====}     )___(
   //                    (\=,      //\\      )__(     /_____\
   //    __    |'-'-'|  //  .\    (    )    /____\     |   |
   //   /  \   |_____| (( \_  \    )__(      |  |      |   |
   //   \__/    |===|   ))  `\_)  /____\     |  |      |   |
   //  /____\   |   |  (/     \    |  |      |  |      |   |
   //   |  |    |   |   | _.-'|    |  |      |  |      |   |
   //   |__|    )___(    )___(    /____\    /____\    /_____\
   //  (====)  (=====)  (=====)  (======)  (======)  (=======)
   //  }===={  }====={  }====={  }======{  }======{  }======={
   // (______)(_______)(_______)(________)(________)(_________)
   //
#include<bits/stdc++.h>
using namespace std;
typedef long long li;
typedef long double ld;
typedef pair<int,int> pt;
typedef pair<ld, ld> ptd;
typedef unsigned long long uli;

#define SORT(vec) sort(vec.begin(), vec.end())
#define loop(i,a,n) for(int i=a;i<n;i++)
#define pb push_back
#define mp make_pair
#define mset(a, val) memset(a, val, sizeof (a))
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define ft first
#define sc second
#define sz(a) int((a).size())
#define x first
#define y second


const int INF = int(1e9);
const li INF64 = li(INF) * li(INF);
const ld EPS = 1e-9;
const ld PI = ld(3.1415926535897932384626433832795);
int main(){
li n;
cin>>n;
for(li i=1;i<=100000;i++){
	li a=i*(i+1)/2;
	if(a>=n){
		cout<<i<<"\n";break;
	}
}
return 0;
}
