/in/foo.c: In function 'main':
/in/foo.c:8:5: warning: array subscript has type 'char' [-Wchar-subscripts]
    a[j]=c;
     ^
/in/foo.c:13:6: warning: array subscript has type 'char' [-Wchar-subscripts]
     s[i]=a[k];
      ^
/in/foo.c:17:5: warning: array subscript has type 'char' [-Wchar-subscripts]
    s[i]=' ';
     ^
/in/foo.c:26:16: warning: array subscript has type 'char' [-Wchar-subscripts]
   printf("%c",s[j]);
                ^