/in/foo.c: In function 'main':
/in/foo.c:6:19: error: expected ')' before 's2'
  scanf("%s %s",s1 s2);
                   ^~
/in/foo.c:6:13: warning: format '%s' expects a matching 'char *' argument [-Wformat=]
  scanf("%s %s",s1 s2);
             ^
/in/foo.c:7:2: warning: implicit declaration of function 'Length' [-Wimplicit-function-declaration]
  Length(s1);
  ^~~~~~
/in/foo.c: At top level:
/in/foo.c:12:6: warning: conflicting types for 'Length'
 void Length(char s[])
      ^~~~~~
/in/foo.c:7:2: note: previous implicit declaration of 'Length' was here
  Length(s1);
  ^~~~~~