foo.cc: In function 'int main()':
foo.cc:61:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   61 |     scanf("%d%d",&N,&M);
      |     ~~~~~^~~~~~~~~~~~~~
foo.cc:63:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   63 |         scanf("%d%d",&a,&b);
      |         ~~~~~^~~~~~~~~~~~~~

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