+51 Find the number of paths from P to Q, where each step is to the right or up.
$[asy]
draw((0,0)--(2,0)--(2,6)--(6,6));
draw((0,0)--(0,3)--(6,3)--(6,6));
draw((0,1)--(2,1));
draw((0,2)--(2,2));
draw((1,0)--(1,3));
draw((3,6)--(3,3));
draw((4,6)--(4,3));
draw((5,6)--(5,3));
draw((2,4)--(6,4));
draw((2,5)--(6,5));
label("$P$",(0,0),SW);
label("$Q$",(6,6),NE);
[/asy]$
