#include <iostream>

int main() {
    using namespace std;
    int a,b,c,k;
    cin >> a >> b >> k >> c;

    if(c != a && c != b) {
        cout << 0 << endl;
        return 0;
    }

    if(a == b)  {
        cout << k << endl;
        return 0;
    }

    long long result = 1;

    for(int i = 1; i <= k; ++i) {
        result *= 2;
        result = result % 1000000007L;
    }

    cout << (((result * (long long)(k)) / (2L)) % 1000000007L) << endl;

    return 0;
}