#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <climits>
#include <cmath>
#include <regex>
#include <queue>

#define rep(i, N) for(int i = 0; i < (N); i++)

using namespace std;

typedef long long ll;

ll H, W, N, K;

signed main() {
    cin >> H >> W >> N >> K;
    ll rem = H + W - 1;
    rem %= N;
    if (rem == K % N) {
        cout << "YES" << endl;
    } else {
        cout << "NO\n";
    }
}