#include using namespace std; using ll = long long; using ull = unsigned long long; using ld = long double; template using vc = vector; template using vvc = vc>; using pi = pair; using vi = vc; using vvi = vvc; #define rep(i,a,b) for (int i = a; i < b; i++) #define irep(i,a,b) for (int i = a; i > b; i--) #define print(n) cout << n << '\n' #define pritn(n) print(n) #define rup(a,b) (a+b-1)/b #define input(A,N) rep(i,0,N) cin>>A[i] #define chmax(a,b) a = max(a,b) #define chmin(a,b) a = min(a,b) int main(){ cout << fixed << setprecision(15); ll a,b,x,n; cin>>a>>b>>x>>n; if(x%2==0) cout<