foo.cc: In function 'int main()':
foo.cc:5:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    5 |     scanf("%d%d",&n,&k);
      |     ~~~~~^~~~~~~~~~~~~~
foo.cc:6:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    6 |     for (int i=1;i<=k;++i) scanf("%d%d",&a[i],&b[i]);
      |                            ~~~~~^~~~~~~~~~~~~~~~~~~~

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