foo.cc: In function 'long long int f(long long int, long long int, long long int, long long int)':
foo.cc:16:19: warning: unused variable 'ans' [-Wunused-variable]
   16 |         long long ans=0;
      |                   ^~~
foo.cc:25:1: warning: no return statement in function returning non-void [-Wreturn-type]
   25 | }
      | ^

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