#include <bits/stdc++.h>
using namespace std;

long long n, m, x, y;
int main() {
    while (cin >> n >> m >> x >> y) {
        --x; --y;
        long long qx = x / m, qy = y / m, rx = x % m, ry = y % m;
        if (qx & 1) rx = m-1 - rx;
        if (qy & 1) ry = m-1 - ry;
        
        //cout << rx << ", " << ry << endl;
        
        if (rx == ry) puts("YES");
        else puts("NO");
    }
}