#include <cstdio>
#include <cstring>
#include <cmath>
#include <cassert>
#include <random>
#include <vector>
#include <algorithm>
#include <array>
#include <functional>
#include <utility>
#include <regex>
#include <tuple>
#include <map>

using namespace std;

int main(){
	int64_t n,m,x,y;
	-scanf("%ld%ld%ld%ld",&n,&m,&x,&y);
	//x--;y--;
	x=x%(m*2);
	if(x>m){
		x=m*2-x+1;
	}
	y=y%(m*2);
	if(y>m){
		y=m*2-y+1;
	}
	puts(x==y?"YES":"NO");
	//printf("%ld,%ld\n",x,y);
	/*
	vector<int> c(m*2);
	for(int i=0;i<m;i++){
		c[i]=c[m*2-i-1]=i;
	}
	puts(c[x%(m*2)]==c[y%(m*2)]?"YES":"NO");
	*/
	return 0;
}