// ABC183C
#include <bits/stdc++.h>
#include <iostream>
#include <cstring>
#include <string>
#include <regex>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <vector>
#include <set>

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define FOR(i, n, m) for(int i = (int)(n); i < (int)(m); i++)
#define SIZE_OF_ARRAY(array) (sizeof(array)/sizeof(array[0]))

using ll = long long;
using namespace std;

int main()
{
    int V, T, S, D;
    cin >> V >> T >> S >> D;
    
    if ((D) == (T * V)) {
        cout << "No" << endl;
    } else if (((D) > (T * V)) && ((D) < (S * V))) {
        cout << "No" << endl;
    } else if ((D) == (S * V)) {
        cout << "No" << endl; 
    } else {
        cout << "Yes" << endl;
    }

    return 0;
} 
#include <iostream>
#include<bits/stdc++.h>
#include <string>
using namespace std;
int main(void){
    int h,w,x,y;
    std::cin >> h >> w >> x >> y;
    x -= 1;
    y -= 1;
    string s[h];
    
    for (int i= 0;i<h;i++){
        std::cin >> s[i];
    }
    
    int cnt = -3;
    // down
    for (int i = x; i < h && s[i][y] != '#'; i++){
        cnt++;
    }
    // up
    for (int i = x; i >= 0 && s[i][y] != '#'; i--){
        cnt++;
    }
    
    // right
    for (int i = y; i < w && s[x][i] != '#'; i++){
        cnt++;
    }
    // left
    for (int i = y; i >= 0 && s[x][i] != '#'; i--){
        cnt++;
    }
    
    std::cout << cnt << std::endl;
}
