View Compilation Error

0_0_25224137_6916.cpp: In function 'int readint()':
0_0_25224137_6916.cpp:23:18: error: 'lastch' was not declared in this scope
  while (!isdigit(lastch) && lastch != '-') lastch = getchar();
                  ^
0_0_25224137_6916.cpp:24:6: error: 'lastch' was not declared in this scope
  if (lastch == '-') {
      ^
0_0_25224137_6916.cpp:29:17: error: 'lastch' was not declared in this scope
  while (isdigit(lastch)) {
                 ^