#include <bits/stdc++.h>
#define r(i,n) for(int i=0;i<n;i++)
#define int long long
using namespace std;
typedef pair<int,int>P;
#define fi first
#define se second


signed main(){
	int h,w,x,y;
	cin>>h>>w>>x>>y;

	int a=h-y,b=y-1;
	int c=w-x,d=x-1;

	if(a%2&&b%2&&c%2==0&&d%2==0 || c%2&&d%2&&a%2==0&&b%2==0)cout<<"No"<<endl;
	else cout<<"Yes"<<endl;
}
