/in/foo.c: In function 'main':
/in/foo.c:8:3: error: case label does not reduce to an integer constant
   case n<=100&&n>=80:printf("A"\n);break;
   ^~~~
/in/foo.c:8:32: error: stray '\' in program
   case n<=100&&n>=80:printf("A"\n);break;
                                ^
/in/foo.c:8:33: error: expected ')' before 'n'
   case n<=100&&n>=80:printf("A"\n);break;
                                 ^
/in/foo.c:9:3: error: case label does not reduce to an integer constant
   case n<=79&&n>=70:printf("B"\n);break;
   ^~~~
/in/foo.c:9:31: error: stray '\' in program
   case n<=79&&n>=70:printf("B"\n);break;
                               ^
/in/foo.c:9:32: error: expected ')' before 'n'
   case n<=79&&n>=70:printf("B"\n);break;
                                ^
/in/foo.c:10:3: error: case label does not reduce to an integer constant
   case n<=69&&n>=60:printf("C"\n);break;
   ^~~~
/in/foo.c:10:31: error: stray '\' in program
   case n<=69&&n>=60:printf("C"\n);break;
                               ^
/in/foo.c:10:32: error: expected ')' before 'n'
   case n<=69&&n>=60:printf("C"\n);break;
                                ^
/in/foo.c:11:3: error: case label does not reduce to an integer constant
   case n<60:print("D"\n);break;
   ^~~~
/in/foo.c:11:13: warning: implicit declaration of function 'print' [-Wimplicit-function-declaration]
   case n<60:print("D"\n);break;
             ^~~~~
/in/foo.c:11:22: error: stray '\' in program
   case n<60:print("D"\n);break;
                      ^
/in/foo.c:11:23: error: expected ')' before 'n'
   case n<60:print("D"\n);break;
                       ^