#include <bits/stdc++.h>
using namespace std;

typedef long long int ll;
typedef double ld;

typedef pair<ll, ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;

#define PB push_back
#define ff first
#define ss second
#define MP make_pair

#define FOR(prom, a, b) for ( ll prom = (a); prom < (ll)b; ++prom)
#define F(a) FOR(i,0,a)
#define FF(a) FOR(j, 0, a)

#define EPS (1e-10)
#define EQ(a, b) (fabs(a-b) <= fabs(a+b)*EPS)
#define LINF (1<<62LL)
#define DEB(x) cerr << ">>> " << #x << " ; " << x << "\n"

int main()
{
    ll a,b,c,k,vys;
    cin >> a >> b >> k >> c;
    if(a == b && a == c)
    {
        cout << k << "\n";
        return 0;
    }
    if(a != c && b != c)
    {
        cout << "0\n";
        return 0;
    }
    if(k == 0)
    {
        cout << "0\n";
        return 0;
    }
    vys = 1;
    F(k-1) 
    {
        vys *= 2;
        vys %= 1000000007;
    }
    vys *= k;
    vys %= 1000000007;
    
    cout << vys << "\n";

return 0;
}