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

int solve(int a, int m){
  a--;
  int kumi;
  if((a / m) % 2 == 0){
    kumi = (a + 1) % m;
  }else{
    kumi = m - ((a + 1) % m);
    kumi++;
  }
  cout << a << " " << kumi << endl;
  return kumi;
}

int main(){
  int n, m, x, y;
  cin >> n >> m >> x >> y;
  
  int kumi_x;
  int kumi_y;

  kumi_x = solve(x, m);
  kumi_y = solve(y, m);
  if(kumi_x == kumi_y){
    cout << "YES" << endl;
  }else{
    cout << "NO" << endl;
  }
}