Untitled

#include <iostream>

using namespace std;

int main() 
{
    int a = 0;
    cin >> a;
    if (a / 1000) - (a % 10) == (a / 100 - (a / 1000 * 10) + (a % 100) - (a % 10)
    {
        cout << "yes";
    }
    else
    {
        cout << "no";
    }
    return 0;
}