#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i, a, n) for (int i = (a); i < (n); i++)
#define per(i, a, n) for (int i = (n) - 1; i >= (a); i--)
#define FOR(i, n) rep(i, 0, (n))
#define fi first
#define se second

//char endl = '\n';

const ll MOD = 1e9 + 7;

int main(void) {
	ios_base::sync_with_stdio(false);
	int a, b, c;
	ll k;
	cin >> a >> b >> k >> c;
	if (k == 0) {
		cout << 0 << endl;
		return 0;
	}
	if (c != a && c != b) {
		cout << 0 << endl;
		return 0;
	}
	int coef = 0;
	if (c==a) coef++;
	if (c==b) coef++;
	ll res = k;
	rep(i,0,k-2+coef) {
		res = (res * 2) % MOD;
	}
	cout << res << endl;
	return 0;
}