foo.c: In function ‘main’:
foo.c:10:28: warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘int’ [-Wformat=]
   10 |                 printf("%d%s",a[i-1],c);
      |                           ~^         ~
      |                            |         |
      |                            char *    int
      |                           %d