#include <bits/stdc++.h>

using namespace std;

int main() {
    int n;
    cin >> n;
    int a = n / 100;
    int b = (n - a * 100) / 10;
    int c = n % 10;
    if (a == b && b == c) cout << "yes" << endl;
    else cout << "no" << endl;
    return 0;
}