#define _USE_MATH_DEFINES
#include<stdio.h>
#include<string>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include<iomanip>

//#include<bits/stdc++.h>



using namespace std;




int main() {
	
	int n,m,x,y;
	cin>>n>>m>>x>>y;
	int a=x/m,b=y/m;
	if(x%m==0)a--;
	if(y%m==0)b--;
	int r,v;
	if(a%2){
		if(x%m==0)r=1;
		else{
			r=m-x%m+1;
		}

	}
	else{
		if(x%m==0)r=m;
		else{
			r=x%m;
		}
	}

	if(b%2){
		if(y%m==0)v=1;
		else{
			v=m-y%m+1;
		}

	}
	else{
		if(y%m==0)v=m;
		else{
			v=y%m;
		}
	}
//	cout<<r<<v;
	if(r==v)cout<<"YES"<<endl;
	else cout<<"NO"<<endl;

	return 0;
}