#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; typedef long long ll; typedef unsigned long long ull; typedef long double ld; typedef pair P; typedef tuple T; typedef vector vec; inline bool check(ll x, ll y, ll xMax, ll yMax) { return x >= 0 && y >= 0 && xMax > x && yMax > y; } inline int toint(string s) { int v; istringstream sin(s); sin >> v; return v; } template inline string tostring(T x) { ostringstream sout; sout << x; return sout.str(); } template inline T sqr(T x) { return x*x; } template inline T mypow(T x, ll n) { T res = 1; while (n > 0) { if (n & 1)res = res * x; x = x * x; n >>= 1; }return res; } inline ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; } inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; } #define For(i,a,b) for(ll (i) = (a);i < (b);(i)++) #define rep(i,n) For(i,0,n) #define rFor(i,a,b) for(ll (i) = (a-1);i >= (b);(i)--) #define rrep(i,n) rFor(i,n,0) #define each(i,n) for(auto &i : n) #define clr(a) memset((a), 0 ,sizeof(a)) #define mclr(a) memset((a), -1 ,sizeof(a)) #define all(a) (a).begin(),(a).end() #define sz(a) (sizeof(a)) #define tostr(a) tostring(a) #define dump(val) cerr << #val " = " << val << endl; #define Fill(a,v) fill((int*)a,(int*)(a+(sz(a)/sz(*(a)))),v) const ll dx[8] = { 1, 0, -1, 0, 1, 1, -1, -1 }, dy[8] = { 0, -1, 0, 1, -1, 1, -1, 1 }; const ll mod = 1e9 + 7; const ll INF = 1e17 + 9; #define int ll #define double ld signed main() { cin.tie(0); ios_base::sync_with_stdio(false); int n, m; cin >> n >> m; int x, y; cin >> x >> y; x--; y--; x = x % (m * 2); y = y % (m * 2); if (x >= m)x = 2 * m - x - 1; if (y >= m)y = 2 * m - y - 1; if (x == y) { cout << "YES" << endl; } else { cout << "NO" << endl; } return 0; }