#include <bits/stdc++.h>
using namespace std;

// template {{{
#define  range(i, l, r) for (int i = (int)(l); i < (int)(r); (i) += 1)
#define rrange(i, l, r) for (int i = (int)(r) - 1; i >= (int)(l); (i) -= 1)

#define  whole(f, x, ...) ([&](decltype((x)) container) { return (f)(  begin(container),  end(container), ## __VA_ARGS__); })(x)
#define rwhole(f, x, ...) ([&](decltype((x)) container) { return (f)( rbegin(container), rend(container), ## __VA_ARGS__); })(x)

#define debug(x) cerr << "(" << __LINE__ << ")" << #x << ": " << (x) << endl

using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;

constexpr i32 mod   = 1e9 + 7;
// constexpr i32 mod   = 998244353;

constexpr i32 inf   = 1001001001;
constexpr i64 infll = 1001001001001001001ll;

constexpr i32 dx[] = {0, -1, 1, 0, -1, 1, -1, 1}; 
constexpr i32 dy[] = {-1, 0, 0, 1, -1, -1, 1, 1};

struct IoSetup { IoSetup(i32 x = 15){ cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(x); cerr << fixed << setprecision(x); } } iosetup;

template <typename T = i64> T input() { T x; cin >> x; return x; }

template <typename T> ostream &operator<<(ostream &os, vector<T> &v) { range(i, 0, v.size()) { os << v[i] << (i + 1 != (int)v.size() ? " " : ""); } return os; } 
template <typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &in : v) is >> in; return is; }

template <typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
template <typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }

template <typename T> vector<T> make_vector(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_vector(size_t a, Ts... ts) { return vector<decltype(make_vector(ts...))>(a, make_vector(ts...)); }

template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
// }}}

void solve() {
  int v, t, s, d;
  cin >> v >> t >> s >> d;

  if (v * t <= d and d <= v * s) {
    cout << "No" << endl;
  } else {
    cout << "Yes" << endl;
  }
}

signed main() {
  solve();
}

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
#define int long long
int lst[3][11];
int nlst[10];

bool check(void) {
    int num[3] = {0};
    for (int i = 0; i < 3; i++) {
        if (nlst[lst[i][0]] == 0) return false;
        for (int j = 0; j < lst[i][10]; j++) {
            num[i] *= 10;
            num[i] += nlst[lst[i][j]];
        }
    }
    return (num[0] + num[1] == num[2]);
}

signed main(void) {
    string s;
    bool b;
    char clst[10];
    int cp = 0;
    for (int i = 0; i < 3; i++) {
        cin >> s;
        for (int j = s.size() - 1; j >= 0; j--) {
            lst[i][10] = s.size();
            b = true;
            // アルファベットを数字に変換
            for (int k = 0; k < cp; k++) {
                if (clst[k] == s[j]) {
                    lst[i][j] = k;
                    b = false;
                    break;
                }
            }
            if (b) {
                if (cp >= 10) {
                    // 11文字以上使われてる
                    cout << "UNSOLVABLE" << endl;
                    return 0;
                }
                clst[cp] = s[j];
                lst[i][j] = cp;
                cp++;
            }
        }
    }

    vector<int> seed = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    sort(seed.begin(), seed.end());
    do {
        for (int i = 0; i < 10; i++) nlst[i] = seed[i];
        b = check();
        if (b) break;
    } while (next_permutation(seed.begin(), seed.end()));

    if (b) {
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < lst[i][10]; j++) cout << nlst[lst[i][j]];
            cout << endl;
        }
    } else
        cout << "UNSOLVABLE" << endl;
}