/in/foo.cc: In function 'int main()':
/in/foo.cc:34:8: warning: variable 'temp' set but not used [-Wunused-but-set-variable]
    int temp;
        ^~~~
/in/foo.cc:17:9: warning: iteration 1000001 invokes undefined behavior [-Waggressive-loop-optimizations]
   sum[i]=0;
   ~~~~~~^~
/in/foo.cc:15:15: note: within this loop
  for(int i=0;i<=1000001;i++)
              ~^~~~~~~~~