#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define REP(i,n) for(long (i)=0;(i)<(n);(i)++) #define FOR(i,a,b) for(long (i)=(a);(i)<(b);(i)++) #define RREP(i,a) for(long (i)=(a)-1;(i)>=0;(i)--) #define FORR(i,a,b) for(long (i)=(a)-1;(i)>=(b);(i)--) #define PI acos(-1.0) #define DEBUG(C) cout< #define VL vector #define VD vector #define PII pair #define PDD pair #define PLL pair #define ALL(a) (a).begin(),(a).end() #define SORT(a) sort(ALL(a)) #define REVERSE(a) reverse(ALL(a)) #define MP make_pair #define FORE(a,b) for(auto &&a:b) using namespace std; typedef long long LL; typedef unsigned long long ULL; const int INF=1e9; const int MOD=INF+7; int main(void) { long N,M; cin>>N>>M; long X,Y; cin>>X>>Y; long XM=X%M,YM=Y%M; X/=M; Y/=M; long XA,YA; if(X&1) XM=M-XM+1; if(Y&1) YM=M-YM+1; if(XM==YM) cout<<"YES"; else cout<<"NO"; cout<