foo.c:1:1: warning: data definition has no type or storage class
 n=int(input())
 ^
foo.c:1:1: warning: type defaults to 'int' in declaration of 'n' [-Wimplicit-int]
foo.c:1:3: error: expected expression before 'int'
 n=int(input())
   ^~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。