foo.cc: In function 'int main()':
foo.cc:11:14: warning: unused variable 'ans' [-Wunused-variable]
  int n,m,i,j,ans=0;
              ^~~
foo.cc:13:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:25:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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