foo.cc: In function 'int main()':
foo.cc:14:12: warning: unused variable 'x' [-Wunused-variable]
   14 |  long long x;
      |            ^
foo.cc:9:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    9 |  freopen("railway.in", "r", stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:10:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   10 |  freopen("railway.out", "w", stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:17:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   17 |   scanf("%lld", &a[i]);
      |   ~~~~~^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务