/in/foo.cc: In function 'int main()':
/in/foo.cc:11:21: warning: iteration 99997u invokes undefined behavior [-Waggressive-loop-optimizations]
   a[i]=a[i-1]+a[i-2];
                     ^
/in/foo.cc:10:15: note: containing loop
  for(int i=3;i<=100000;++i){
               ^