View Compilation Error

0_0_18493034_6498.cpp: In function 'int main()':
0_0_18493034_6498.cpp:46:16: error: 'num_city' was not declared in this scope
  while (cin >> num_city >> num_road)
                ^
0_0_18493034_6498.cpp:46:28: error: 'num_road' was not declared in this scope
  while (cin >> num_city >> num_road)
                            ^