foo.cc: In function 'int main()':
foo.cc:21:29: warning: unused variable 'mid' [-Wunused-variable]
   21 |  int a[N],n,i,key,start,end,mid,num=0,index;
      |                             ^~~
foo.cc:21:33: warning: unused variable 'num' [-Wunused-variable]
   21 |  int a[N],n,i,key,start,end,mid,num=0,index;
      |                                 ^~~
foo.cc:31:2: warning: 'index' is used uninitialized in this function [-Wuninitialized]
   31 |  if(index==-1)
      |  ^~

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