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