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

//size_t factorial(int k, int i) {
//    size_t result = 1;
//    if (i < k - i) i = k - i;
//    for (int j = k; j > i; j--) {
//        result *= j;
//    }
//    for (int j = k - i; j > 0; j--) {
//        result /= j;
//    }
//    return result;
//}
//

size_t factorial(int k, int i) {
    size_t result = 1;
    size_t div = 1;

    if (i > k - i) {
        for (int j = i + 1; j <= k; j++) {
            result *= j;
        }
        for (int j = 2; j <= k - i; j++) {
            div *= j;
        }
    } else {
        for (int j = k-i + 1; j <= k; j++) {
            result *= j;
        }
        for (int j = 2; j <= i; j++) {
            div *= j;
        }
    }

//    std::cout << k << " " << i << " " << result << " " << div << "\n";
//    std::cout << (float ) result / div << "\n";

    result /= div;

    return result;
}



using namespace std;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);

    int a, b, k, c;

    cin >> a >> b >> k >> c;

    if (c == a && c == b) {
        cout << k << endl;
        return 0;
    }

    if (c != a && c != b) {
        cout << 0 << endl;
        return 0;
    }

    size_t result = 0;
    for (int i = 1; i <= k; i++) {
        result += i * factorial(k, i);
    }

    result = result % 1000000007;

    cout << result << endl;

    return 0;
}