#!/usr/bin/env python3

from math import factorial

def bin(n, k):
    if k > n:
        return 0
    return factorial(n) // (factorial(n-k)*factorial(k))

def strings(k):
    k -= 2
    s = 0
    for inter in range(25):
        for i in range(0,k+1):
            s += (25-inter) * 2**i * bin(inter, i) * bin(24-inter, k-i)
    return s

print(max((2**k - k - 1) * bin(26, k) for k in range(2, 27)))