/in/foo.cc: In function 'bool check(ll)':
/in/foo.cc:68:27: error: 'memset' was not declared in this scope
  memset(vis, 0, sizeof vis);
                           ^
/in/foo.cc: In function 'll solve()':
/in/foo.cc:103:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   ll mid = l + r >> 1;
            ~~^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:111:18: error: 'scanf_s' was not declared in this scope
  scanf_s("%d", &n);
                  ^
/in/foo.cc:112:30: error: 'memset' was not declared in this scope
  memset(head, -1, sizeof head);
                              ^