foo.c: In function 'main':
foo.c:9:20: warning: comparison of constant '30' with boolean expression is always true [-Wbool-compare]
   if(i%10==2||20<=i<30)
                    ^
foo.c:9:17: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
   if(i%10==2||20<=i<30)
               ~~^~~
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d",&a,&b);
  ^~~~~~~~~~~~~~~~~~~~

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