Traveler has just stolen Furina's favorite dessert, and now Furina is frantically searching for the damn traveler in the whole Fontaine!
Fontaine is a country composed of grids of

rows and

columns with rows numbered

and columns numbered

. Our poor traveler is now in the grid with coordinate
at time 
, and expacts to reach the grid with coordinate
)
so that he could escape from
Fontaine. During each moment, traveler
can only move downwards or rightwords for
any number of grids.
In order to catch traveler, Furina calls

inspectors who are scheduled to reach
)
at

to catch traveler, as long as traveler
arrives, passes through, or leaves
when or after 
, he will be caught! In addtion,
Furina will close the gate of Fontaine after time
, if traveler haven't escaped before that, he will never be able to escape!
However, traveler is a math lover, so in any cases of crisis, as long as not being caught, he'd like to figure out his fastest scheme to escape, and how many schemes are there in total.
Annotation:Different travel schemes are distinguished based on the direction and distance of escaping, which is not required to be identical every moments. For instance, even if the route is the same, a difference in the execution can still result in distinct schemes.