#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)*K;
    if(A==B)
        out =(out)%(long long)1000000007;
    else
        out = (out/2)%(long long)1000000007;
    cout << out << endl;



    return 0;
}