/in/foo.cc: In function 'int main()':
/in/foo.cc:19:43: warning: iteration 1000009 invokes undefined behavior [-Waggressive-loop-optimizations]
     for(int i = 1;i <= 10000005;i++) f[i] = i;
                                      ~~~~~^~~
/in/foo.cc:19:21: note: within this loop
     for(int i = 1;i <= 10000005;i++) f[i] = i;
                   ~~^~~~~~~~~~~