foo.cc: In function 'int main()':
foo.cc:6:14: warning: unused variable 'j' [-Wunused-variable]
  int n,lim,i,j,ans,step,x,y,tmp;
              ^
foo.cc:7:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~

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