foo.cc: In function 'int main()':
foo.cc:30:10: warning: unused variable 'n1' [-Wunused-variable]
  int num,n1,n2,L,k,n;
          ^~
foo.cc:35:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&x);
   ~~~~~^~~~~~~~~
foo.cc:55:6: warning: 'num' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<num;
  ~~~~^~~~~

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