#include using namespace std; typedef long long ll; typedef vector vi; typedef pair pii; #define pb push_back #define mp make_pair #define fi first #define se second int main() { int n,m,a,b,H,T; cin>>n>>m>>a>>b; int p=a/n,q=a%n; int pp=b/n,qq=b%n; if(q) { if(p%2)H=m-p; else H=p; } else { if(p%2)H=m+1; else H=1; } if(qq) { if(pp%2)T=m-pp+1; else T=pp; } else { if(pp%2)T=m; else T=1; } if(H==T)cout<<"YES"<