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

int main()
{
  int a, b, k, c, i;
  unsigned long l=1;
  scanf("%d %d %d %d", &a, &b, &k, &c);
  if((a == c) || (b == c)) {
    if(a==b) {
      l = k;
    } else {
      for(i=1; i<k; i++) {
        l *= 2; 
        l = l % 1000000007;
      }
      l *= k;
      l = l % 1000000007;
    }
    printf("%lu\n", l);
  } else {
    printf("0\n");
  }

  return(0);
}