import std.stdio, std.string, std.conv, std.range;
import std.algorithm, std.array, std.typecons, std.container;
import std.math, std.numeric, std.random, core.bitop;

enum inf = 1_001_001_001;
enum infl = 1_001_001_001_001_001_001L;

void main() {
    int a, b, c, d;
    scan(a, b, c, d);

    foreach (i; 0 .. 1000) {
        if (a <= 0 || c <= 0) break;
        if (i % 2 == 0) {
            c -= b;
        }
        else {
            a -= d;
        }
    }

    yes(c <= 0);
}

void scan(T...)(ref T args) {
    auto line = readln.split; // @suppress(dscanner.suspicious.unmodified)
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront;
    }
    assert(line.empty);
}

void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}

bool chmin(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args)
        if (x > arg) {
            x = arg;
            isChanged = true;
        }
    return isChanged;
}

bool chmax(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args)
        if (x < arg) {
            x = arg;
            isChanged = true;
        }
    return isChanged;
}

void yes(bool ok, string y = "Yes", string n = "No") {
    return writeln(ok ? y : n);
}
