<?xml version="1.0"?>
<!DOCTYPE billion [
<!ELEMENT billion (#PCDATA)>
<!ENTITY laugh0 "ha">
<!ENTITY laugh1 "&laugh0;&laugh0;">
<!ENTITY laugh2 "&laugh1;&laugh1;">
<!ENTITY laugh3 "&laugh2;&laugh2;">
<!ENTITY laugh4 "&laugh3;&laugh3;">
<!ENTITY laugh5 "&laugh4;&laugh4;">
<!ENTITY laugh6 "&laugh5;&laugh5;">
<!ENTITY laugh7 "&laugh6;&laugh6;">
<!ENTITY laugh8 "&laugh7;&laugh7;">
<!ENTITY laugh9 "&laugh8;&laugh8;">
<!ENTITY laugh10 "&laugh9;&laugh9;">
<!ENTITY laugh11 "&laugh10;&laugh10;">
<!ENTITY laugh12 "&laugh11;&laugh11;">
<!ENTITY laugh13 "&laugh12;&laugh12;">
<!ENTITY laugh14 "&laugh13;&laugh13;">
<!ENTITY laugh15 "&laugh14;&laugh14;">
<!ENTITY laugh16 "&laugh15;&laugh15;">
<!ENTITY laugh17 "&laugh16;&laugh16;">
<!ENTITY laugh18 "&laugh17;&laugh17;">
<!ENTITY laugh19 "&laugh18;&laugh18;">
<!ENTITY laugh20 "&laugh19;&laugh19;">
<!ENTITY laugh21 "&laugh20;&laugh20;">
<!ENTITY laugh22 "&laugh21;&laugh21;">
<!ENTITY laugh23 "&laugh22;&laugh22;">
<!ENTITY laugh24 "&laugh23;&laugh23;">
<!ENTITY laugh25 "&laugh24;&laugh24;">
<!ENTITY laugh26 "&laugh25;&laugh25;">
<!ENTITY laugh27 "&laugh26;&laugh26;">
<!ENTITY laugh28 "&laugh27;&laugh27;">
<!ENTITY laugh29 "&laugh28;&laugh28;">
<!ENTITY laugh30 "&laugh29;&laugh29;">
]>
<billion>&laugh30;</billion>