/in/foo.cc: In function 'int main()':
/in/foo.cc:21:8: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<sum<<endl;
        ^~~
/in/foo.cc:16:11: warning: 'max' may be used uninitialized in this function [-Wmaybe-uninitialized]
   if(a[max]<a[i]) max=i;
      ~~~~~^