#include <bits/stdc++.h>   using namespace std;   long long z, mn, mx, sum, ans, k, pos, pos1, r, xx, yy, zz, n, m, x, y;   vector<int> v;   bool OK[1000002], KO[1000002], zoom;   int b[100003], c[100002];   map<char, int> mp, mr;   set<int> st;   int main() {     cin >> n;     for (int i = 0; i < n; ++i) {       cin >> x >> y >> k;       cout << ((k + 1) / 2 * x) - (k / 2 * y) <<   n ;     }   }   