View Compilation Error

0_0_39597091_1157.cpp: In function 'int read()':
0_0_39597091_1157.cpp:42:16: error: 'isdigit' was not declared in this scope
   42 |         while(!isdigit(ch)){
      |                ^~~~~~~
0_0_39597091_1157.cpp:46:15: error: 'isdigit' was not declared in this scope
   46 |         while(isdigit(ch)){
      |               ^~~~~~~