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

#define int long long

#define MOD 1000000007

int pow_mod(int x, int p) {
	int r = 1;
	while (p > 0) {
		if (p % 2 == 1) {
			r *= x;
			r %= MOD;
		}
		p /= 2;
		x *= x;
		x %= MOD;
	}
	return r;
}

int inv_mod(int x) {
	return pow_mod(x, MOD - 2);
}

int fac_mod(int x) {
	static vector<int> v = { 1 };
	while (v.size() - 1 < x) {
		v.push_back(v.back() * v.size() % MOD);
	}
	return v[x];
}

int inv_fac_mod(int x) {
	static vector<int> v = { 1 };
	while (v.size() - 1 < x) {
		v.push_back(v.back() * inv_mod(v.size()) % MOD);
	}
	return v[x];
}

int bin_mod(int n, int k) {
	if (k < 0 || k > n) {
		return 0;
	}
	return fac_mod(n) * inv_fac_mod(n - k) % MOD * inv_fac_mod(k) % MOD;
}

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
#ifdef CB
	freopen("in.txt", "r", stdin);
//	freopen("out.txt", "w", stdout);
#endif
	int N, M, P, R;
	cin >> N >> M >> P >> R;
	int r = N / P, c = M / P;
	int ans = bin_mod(N + M, N) - bin_mod(r + c, r) + MOD;
	ans %= MOD;
	ans *= inv_mod(P);
	ans %= MOD;
	cout << ans << '\n';
	return 0;
}