#include <iostream>
#define LL long long

using namespace std;

int main()
{
    LL A, B, K, C;
    cin >> A >> B >> K >> C;
    if (C != A && C != B) {
        cout << 0 << endl;
        return 0;
    }

    if (K == 0) {
        cout << 0 << endl;
        return 0;
    } else if (K == 1) {
        cout << 1 << endl;
        return 0;
    }
    LL out = 1;
    for (LL i = 0; i < K - 1; ++i) {
        out *= 2;
        out %= 1000000007;
    }
    cout << (out * K) % 1000000007 << endl;
    return 0;
}