<?php
$a=10;
$b=5;
for ($i=1; $i>=1000; $i++){
if ($a <$b){
echo "$a $b";
}elseif($a>20){
$a=$a+1;
$b=$b+2;
echo "$a $b";
}else{
$a=$a+5;
$b=$b-1;
echo "$a $b";
}
}
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