foo.cc: In function 'int main()':
foo.cc:65:44: warning: iteration 1004 invokes undefined behavior [-Waggressive-loop-optimizations]
   65 |         for(int i = 1;i <= N;i ++) head[i] = -1;
      |                                    ~~~~~~~~^~~~
foo.cc:65:25: note: within this loop
   65 |         for(int i = 1;i <= N;i ++) head[i] = -1;
      |                       ~~^~~~
foo.cc:66:42: warning: iteration 1004 invokes undefined behavior [-Waggressive-loop-optimizations]
   66 |         for(int i = 1;i <= N;i ++) fa[i] = i;
      |                                    ~~~~~~^~~
foo.cc:66:25: note: within this loop
   66 |         for(int i = 1;i <= N;i ++) fa[i] = i;
      |                       ~~^~~~
foo.cc:65:44: warning: 'void* __builtin_memset(void*, int, long unsigned int)' forming offset [4020, 4023] is out of the bounds [0, 4020] of object 'head' with type 'int [1005]' [-Warray-bounds]
   65 |         for(int i = 1;i <= N;i ++) head[i] = -1;
      |                                    ~~~~~~~~^~~~
foo.cc:15:13: note: 'head' declared here
   15 | int fa[N] , head[N] , cnt;
      |             ^~~~

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