foo.c:1:1: warning: data definition has no type or storage class
 n=input()
 ^
foo.c:1:1: warning: type defaults to 'int' in declaration of 'n' [-Wimplicit-int]
foo.c:1:3: warning: implicit declaration of function 'input' [-Wimplicit-function-declaration]
 n=input()
   ^~~~~
foo.c:1:3: error: initializer element is not constant
foo.c:2:1: error: expected ',' or ';' before 'ans'
 ans=0
 ^~~

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