#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define REP(i,a,b) for(int i=a;i<(int)b;i++) #define rep(i,n) REP(i,0,n) #define all(c) (c).begin(), (c).end() #define zero(a) memset(a, 0, sizeof a) #define minus(a) memset(a, -1, sizeof a) #define watch(a) { cout << #a << " = " << a << endl; } template inline bool minimize(T1 &a, T2 b) { return b < a && (a = b, 1); } template inline bool maximize(T1 &a, T2 b) { return a < b && (a = b, 1); } typedef long long ll; int const inf = 1<<29; int main() { ll H, W, N, K; cin >> H >> W >> N >> K; cout << ((H+W-2)%N+1 == K ? "YES\n":"NO\n"); return 0; }