foo.cc: In function 'int main()':
foo.cc:29:29: warning: unused variable 'mid' [-Wunused-variable]
   29 |  int a[N],n,i,key,start,end,mid,num=0,index;
      |                             ^~~
foo.cc:29:33: warning: unused variable 'num' [-Wunused-variable]
   29 |  int a[N],n,i,key,start,end,mid,num=0,index;
      |                                 ^~~

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