/in/foo.cc: In function 'int main()':
/in/foo.cc:14:21: warning: iteration 19999u invokes undefined behavior [-Waggressive-loop-optimizations]
    a[i]=count+a[i-1];
                     ^
/in/foo.cc:6:12: note: containing loop
   for(i=1;i<=20000;i++){
            ^