foo.cc: In function 'int main()':
foo.cc:43:5: warning: unused variable 'l' [-Wunused-variable]
  ll l = 1, r = 1e18;
     ^
foo.cc:43:12: warning: unused variable 'r' [-Wunused-variable]
  ll l = 1, r = 1e18;
            ^
foo.cc:40:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld", &k);
  ~~~~~^~~~~~~~~~~~

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