/in/foo.cc: In function 'int main()':
/in/foo.cc:16:36: warning: iteration 1499999 invokes undefined behavior [-Waggressive-loop-optimizations]
     for(int i=1;i<=1500000;i++)a[i]=i;
                                ~~~~^~
/in/foo.cc:16:18: note: within this loop
     for(int i=1;i<=1500000;i++)a[i]=i;
                 ~^~~~~~~~~