/in/foo.c: In function 'main':
/in/foo.c:15:10: warning: array subscript has type 'char' [-Wchar-subscripts]
  while((s[i]=getchar())!='\n')
          ^
/in/foo.c:17:3: warning: array subscript has type 'char' [-Wchar-subscripts]
  s[i]='\0';
   ^
/in/foo.c:18:11: warning: array subscript has type 'char' [-Wchar-subscripts]
  while((st[j]=getchar())!='\n')
           ^
/in/foo.c:20:4: warning: array subscript has type 'char' [-Wchar-subscripts]
  st[j]='\0';
    ^