/in/foo.cc: In function 'int main()':
/in/foo.cc:340:24: warning: format '%s' expects argument of type 'char*', but argument 3 has type 'char (*)[300]' [-Wformat=]
  scanf("%d\n%s", &n, &a);
                        ^
/in/foo.cc:344:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0;i < strlen(a);i ++)
             ~~^~~~~~~~~~~
/in/foo.cc:338:9: warning: unused variable 'j' [-Wunused-variable]
  int i, j;
         ^