1<?xml version="1.0"?> 2<!DOCTYPE billion [ 3<!ELEMENT billion (#PCDATA)> 4<!ENTITY laugh0 "ha"> 5<!ENTITY laugh1 "&laugh0;&laugh0;"> 6<!ENTITY laugh2 "&laugh1;&laugh1;"> 7<!ENTITY laugh3 "&laugh2;&laugh2;"> 8<!ENTITY laugh4 "&laugh3;&laugh3;"> 9<!ENTITY laugh5 "&laugh4;&laugh4;"> 10<!ENTITY laugh6 "&laugh5;&laugh5;"> 11<!ENTITY laugh7 "&laugh6;&laugh6;"> 12<!ENTITY laugh8 "&laugh7;&laugh7;"> 13<!ENTITY laugh9 "&laugh8;&laugh8;"> 14<!ENTITY laugh10 "&laugh9;&laugh9;"> 15<!ENTITY laugh11 "&laugh10;&laugh10;"> 16<!ENTITY laugh12 "&laugh11;&laugh11;"> 17<!ENTITY laugh13 "&laugh12;&laugh12;"> 18<!ENTITY laugh14 "&laugh13;&laugh13;"> 19<!ENTITY laugh15 "&laugh14;&laugh14;"> 20<!ENTITY laugh16 "&laugh15;&laugh15;"> 21<!ENTITY laugh17 "&laugh16;&laugh16;"> 22<!ENTITY laugh18 "&laugh17;&laugh17;"> 23<!ENTITY laugh19 "&laugh18;&laugh18;"> 24<!ENTITY laugh20 "&laugh19;&laugh19;"> 25<!ENTITY laugh21 "&laugh20;&laugh20;"> 26<!ENTITY laugh22 "&laugh21;&laugh21;"> 27<!ENTITY laugh23 "&laugh22;&laugh22;"> 28<!ENTITY laugh24 "&laugh23;&laugh23;"> 29<!ENTITY laugh25 "&laugh24;&laugh24;"> 30<!ENTITY laugh26 "&laugh25;&laugh25;"> 31<!ENTITY laugh27 "&laugh26;&laugh26;"> 32<!ENTITY laugh28 "&laugh27;&laugh27;"> 33<!ENTITY laugh29 "&laugh28;&laugh28;"> 34<!ENTITY laugh30 "&laugh29;&laugh29;"> 35]> 36<billion>&laugh30;</billion> 37