func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       long long n, a, b;       cin >> a >> b >> n;       if (n % 2 == 0)         cout << (n / 2) * (a - b) << endl;       else         cout << ((n / 2) * (a - b)) + a << endl;     }     return 0;   }   