/in/foo.c:1:1: warning: data definition has no type or storage class
 s=0
 ^
/in/foo.c:1:1: warning: type defaults to 'int' in declaration of 's' [-Wimplicit-int]
/in/foo.c:2:1: error: expected ',' or ';' before 'n'
 n=int(input())
 ^