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

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define all(x) (x).begin(),(x).end()
using ll = long long;
string char_to_string(char val) {
  return string(1, val);
}
int char_to_int(char val) {
  return val - '0';
}
template<class T> inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template<class T> inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
int vector_finder(std::vector<ll> vec, int number) {
  auto itr = std::find(vec.begin(), vec.end(), number);
  size_t index = std::distance( vec.begin(), itr );
  if (index != vec.size()) { // 発見できたとき
    return 1;
  }
  else { // 発見できなかったとき
    return 0;
  }
}

int main() {
  int sx, sy, tx, ty; cin >> sx >> sy >> tx >> ty;
  int x = tx - sx; int y = ty - sy;
  vector<string> ans;
  REP(i, y) ans.push_back("U");
  REP(i, x) ans.push_back("R");
  REP(i, y) ans.push_back("D");
  REP(i, x) ans.push_back("L");
  ans.push_back("L");
  REP(i, y + 1) ans.push_back("U");
  REP(i, x + 1) ans.push_back("R");
  ans.push_back("D");
  ans.push_back("R");
  REP(i, y + 1) ans.push_back("D");
  REP(i, x + 1) ans.push_back("L");
  ans.push_back("U");
  REP(i, ans.size()) cout << ans[i];
  cout << endl;
}
#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm> 
#include <cmath>

using namespace std;

typedef long long LL;

const int MOD = 1000000007;
const int MAXN = 2 * 100005;

LL H, W;
LL A, B;
LL fact[MAXN];

// Exponentiation by squaring
LL expsq(LL x, LL p) {
	LL res = 1;
	while (p > 0) {
		if (p & 1) {
			res = (res * x) % MOD;
		}
		x = (x * x) % MOD;
		p /= 2;
	}
	return res;
}

// Extended Euler's algorithm
LL modinv(LL x) {
	return expsq(x, MOD - 2);
}

LL C(LL n, LL k) {
	return (fact[n] * modinv(fact[n - k] * fact[k] % MOD)) % MOD;
}

int main() {
	cin >> H >> W >> A >> B;
	fact[0] = 1;
	for (int i = 1; i < MAXN; i++) {
		fact[i] = fact[i - 1] * i;
		fact[i] %= MOD;
	}

	LL ans = 0;
	for (LL i = B; i <= W - 1; i++) {
		LL res = C(H - A - 1 + i, i);
		LL end = C(W - i - 1 + A - 1, A - 1);
		res *= end;
		res %= MOD;

		ans += res;
		ans %= MOD;
	}

	cout << ans << endl;
}