foo.cc: In function 'int main()':
foo.cc:22:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |     scanf("%d", &n);//输入指令次数
      |     ~~~~~^~~~~~~~~~
foo.cc:35:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   35 |         scanf("%d%d", &a, &b);
      |         ~~~~~^~~~~~~~~~~~~~~~
foo.cc:27:14: warning: iteration 30009 invokes undefined behavior [-Waggressive-loop-optimizations]
   27 |         p[i] = i;
      |         ~~~~~^~~
foo.cc:26:23: note: within this loop
   26 |     for (int i = 1; i <= N;i++) {
      |                     ~~^~~~

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