/in/foo.cc: In function 'void init()':
/in/foo.cc:23:22: warning: iteration 100004 invokes undefined behavior [-Waggressive-loop-optimizations]
         f[i][0]=num[i];
                 ~~~~~^
/in/foo.cc:21:19: note: within this loop
     for (int i=1;i<=N;i++)
                  ~^~~