foo.cc: In function 'int main()':
foo.cc:8:7: warning: statement has no effect [-Wunused-value]
  for(a;a<=b;a++)
       ^
foo.cc:6:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &a, &b);
  ~~~~~^~~~~~~~~~~~~~~~~

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