/in/foo.cc: In function 'void febonacci()':
/in/foo.cc:12:8: warning: iteration 1002 invokes undefined behavior [-Waggressive-loop-optimizations]
   s[i] = s[i-1] + s[i-2];
   ~~~~~^~~~~~~~~~~~~~~~~
/in/foo.cc:11:16: note: within this loop
  for(int i=3; i<=maxn; i++)
               ~^~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:20:8: warning: iteration 1003 invokes undefined behavior [-Waggressive-loop-optimizations]
   s[i] += s[i-1];
   ~~~~~^~~~~~~~~
/in/foo.cc:19:16: note: within this loop
  for(int i=2; i<=maxn; i++)
               ~^~~~~~