View Compilation Error

0_0_38609903_21370.cpp: In function 'int read()':
0_0_38609903_21370.cpp:14:44: error: 'f' was not declared in this scope
  for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-f;
                                            ^
0_0_38609903_21370.cpp:16:16: error: 'f' was not declared in this scope
  return read_x*f;
                ^