#include #include #include #include #include #include #include #include #include #include #include #include #include #define p(s) cout<<(s)<=n;i--) #define CK(n,a,b) ((a)<=(n)&&(n)<(b)) #define F first #define S second typedef long long ll; using namespace std; const int inf=1e9+7; int H,W,N,K; int main(){ cin>>H>>W>>N>>K; if((H+W-2)%N==(K-1)%N){ p("YES"); }else{ p("NO"); } return 0; }