#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;
    }

    unsigned long long result = 1;

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

    long long finalResult = (long long)result * (long long)k / 2L;

    int resultToPrint = (int) (finalResult % 1000000007L);
    cout <<  resultToPrint << endl;

    return 0;
}