foo.cc:6:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
    6 | main()
      |      ^
foo.cc: In function 'int main()':
foo.cc:8:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    8 | scanf("%d%d",&n,&m);
      | ~~~~~^~~~~~~~~~~~~~
foo.cc:9:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    9 | for(int i=0;i<=n;i++)scanf("%d",&a[i]);
      |                      ~~~~~^~~~~~~~~~~~

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