Mã chấm: 15307

Main.cc: In function ‘void solve()’:
Main.cc:2:15: error: ‘cin’ was not declared in this scope
  int a, b, x; cin >> a >> b >> x;
               ^~~
Main.cc:3:5: error: ‘cout’ was not declared in this scope
     cout << 3*x - a - b;
     ^~~~