#include #include using namespace std; int main() { short a, b, k, c; int result; cin >> a >> b >> k >> c; if (c != a && c != b) { result = 0; } else if (c == a && a == b) { result = k; } else { result = (int)(pow(2, k - 1) * k) % 1000000007; } cout << result << endl; return 0; }