#include <iostream>
#include <math.h>
#include <cmath>

int main() {
    int a, b, c, k;
    std::cin >> a;
    std::cin >> b;
    std::cin >> k;
    std::cin >> c;
    unsigned long long x = 2;
    unsigned long long modulos = 0;
    for (int i = 0; i < k - 1; i++) {
        x *= 2;
        if (x >= 1000000007) {
            x = x % 1000000007;
            modulos++;
        }
    }
    x = x * k;
    x = x / 2;
    if (modulos > 0) {
        x *= modulos;
    }
    x = x % 1000000007;
    std::cout << x << std::endl;
    return 0;
}