#include <iostream>
#include <string>
#include <sstream>
#include <math.h>
using namespace std;

int main () {
    long long a,b,k,c;
    cin >> a;
    cin >> b;
    cin >> k;
    cin >> c;

    if (c!=a && c!=b) {
        cout<<"0"<<endl;
        return 0;
    }
    long long mod = 1000000007L;
    long long res = ((pow(2,k)*k)/2);
    res %= mod;
    cout << res<< endl;

    return 0;
}