#include <bits/stdc++.h>
using namespace std;
#define ll long long
const ll p = 1000000007;
int main(){
ll a,b,k,c;
ll pow[1001];
pow[0]=1;
for(int i=1;i<=1000;i+=1){
  pow[i]=(pow[i-1]*2)%p;
}
scanf("%lld%lld%lld%lld",&a,&b,&k,&c);
if(k==0){
  printf("0\n");
  return 0;
}
if(a == b){
  if(a == c){
    printf("%lld\n",k);
  }else{
    printf("0\n");
  }
}else{
  if((a ==c) || (b ==c)){
    printf("%lld\n",(pow[k-1]*k)%p);
  }else{
    printf("0\n");
  }
}


return 0;
}