#!/usr/bin/python
 
# Project Euler - Problem 15
 
print "\nProject Euler - Problem 15"
print "Find the number of paths in a 20x20 grid to the bottom right corner.\n"
 
x= []
grid = 20
 
for i in xrange(grid+1):
    x.append([1])
    x[0].append(1)
 
for m in range(1,grid+1):
   for n in range(1,grid+1):
       x[m].append(x[m-1][n] + x[m][n-1])
 
print x[grid][grid]