foo.cc: In function 'void input()':
foo.cc:5:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 #define s(x) scanf("%lld",&(x))
              ~~~~~^~~~~~~~~~~~~
foo.cc:17:2: note: in expansion of macro 's'
  s(n);
  ^
foo.cc:5:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 #define s(x) scanf("%lld",&(x))
              ~~~~~^~~~~~~~~~~~~
foo.cc:19:3: note: in expansion of macro 's'
   s(a[i]);
   ^