#include <iostream>
#include <cmath>

using namespace std;
int main() {
    long long A,B,K,C, out;
    cin >> A >> B >> K >> C;
    string line;
    getline(cin, line);
    out = (long long) pow(2, K-1)*K;
    if(A!=C && B!=C ){
        out = 0;
    }else if(A==B) {
        out = (K) % (long long) 1000000007;
    }else {
        out = (out) % (long long) 1000000007;
    }
    cout << out << endl;



    return 0;
}