vectors E and N exactly and times, respectively. As such, the problem reduces to finding the number of distinct rearrangements of the word , which is equivalent to finding the number of ways to choose indistinct objects from a group of . Thus the total number of paths Fred could take from A to B traveling only blocks is Other problems with known block walking combinatorial proofs Proving that can be done with a straightforward application of block walking. See also Lattice path References Combinatorics