foo.cc: In function 'int main()':
foo.cc:19:9: error: 'ans' was not declared in this scope; did you mean 'abs'?
   19 |         ans=0;
      |         ^~~
      |         abs
foo.cc:20:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   20 |         scanf("%lld%lld",&a,&b);
      |         ~~~~~^~~~~~~~~~~~~~~~~~

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