1+1/(1+2)+1/(1+2+3)+.+1/(1+2+3+4+5+.+2002+2003)
=2/1*2+2/2*3+2/3*4+...+2/2003*2004
=2(1-1/2+1/2-1/3+...+1/2003-1/2004)
=2(1-1/2004)
=2003/1002
1+1/(1+2)+1/(1+2+3)+.+1/(1+2+3+4+5+.+2002+2003)
=2/1*2+2/2*3+2/3*4+...+2/2003*2004
=2(1-1/2+1/2-1/3+...+1/2003-1/2004)
=2(1-1/2004)
=2003/1002