//#include <atcoder/all>
//using namespace atcoder;
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, n) for(int i=0; i<n; i++)
#define REPR(i, n) for(int i=n-1; i>=0; i--)
#define FOR(i, m, n) for(int i=m; i<n; i++)
#define ALL(v) v.begin(), v.end()
#define bit(n) (1LL<<(n))
#define FIX(d) fixed << setprecision(d)
using P = pair<int, int>;
using LP = pair<ll, ll>;
using Graph = vector<vector<int>>;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = 1e9;
const ll LINF = (1LL<<60);

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int v,t,s,d;
  cin >> v >> t >> s >> d;
  if(v*t<=d && d<=v*s) cout << "No\n";
  else cout << "Yes\n";
  
  return 0;
}

#include <bits/stdc++.h>
using namespace std;
#define _GLIBCXX_DEBUG
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using ll = long long;

bool can_go(int x, int y, vector<vector<char>> s) {
    if(s[x][y] == '.') return true;
    else return false;
}

int main() {
    int h, w, x, y;
    cin >> h >> w >> x >> y;
    x--; y--;
    vector<vector<char>> s(h, vector<char> (w));
    rep(i, h) {
        rep(j, w) cin >> s[i][j];
    }

    int ans = 1;
    int s_x = x;
    int s_y = y;

    // turn right
    while (1){
        y++;
        if(y < w) {
            if(can_go(x, y, s)) ans++;
            else break;
        }
        else break;  
    }
    x = s_x;
    y = s_y;
    // turn left
    while (1){
        y--;
        if(-1 < y) {
            if(can_go(x, y, s)) ans++;
            else break;
        }
        else break;  
    }
    x = s_x;
    y = s_y;
    // up
    while (1){
        x--;
        if(-1 < x) {
            if(can_go(x, y, s)) ans++;
            else break;
        }
        else break;  
    }
    x = s_x;
    y = s_y;
    // down
    while (1){
        x++;
        if(x < h) {
            if(can_go(x, y, s)) ans++;
            else break;
        }
        else break;  
    }
    cout << ans << endl;
    return 0;
}