/in/foo.cc: In function 'int main()':
/in/foo.cc:11:21: warning: iteration 997 invokes undefined behavior [-Waggressive-loop-optimizations]
   11 |                 f[i]=f[i-1]+f[i-2];
      |                 ~~~~^~~~~~~~~~~~~~
/in/foo.cc:10:22: note: within this loop
   10 |         for(int i=3;i<=N;i++){
      |                      ^