#include <cstdio>

int main(){
  int a,b,k,c;
  long long r=1;
  scanf("%d %d %d %d",&a,&b,&k,&c);
  if ((k==0) || ((c!=a) && (c!=b))){
    printf("%d\n",0);
    return 0;
  }
  if (a==b){
    printf("%d\n",1);
    return 0;
  }
  for (int i=1;i<=k;++i){
    r=(r*2) % 1000000007;
  }
  r=(r*k) % 1000000007;
  printf("%lld\n",r/2);
  return 0;
}