#include<stdio.h>
#include<iostream>
#include<iomanip>
#include<fstream>
#include<cstdlib>
#include<string.h>
#include<cmath>
using namespace std;
int main()
{
    char A[130];
    while (cin >> A)
    {
        int s=0;
        for (int i = 0; A[i] != '\0'; i++)
        {
            if (A[i] == '-')
                i++;
            s += A[i] - '0';
        }
        if (s % 3 == 0)
            cout << "yes" << endl;
        else
            cout << "no" << endl;
        memset(A, 0, sizeof(A));
    }
}