K = int(input())
S = len(input())

M = 10**9 + 7

F = [1]
IF = [1]
for i in range(1, K + S + 1):
    F.append((F[-1] * i) % M)
    IF.append((IF[-1] * pow(i, M - 2, M)) % M)

def nCr(n, r):
    return (F[n] * IF[r] * IF[n-r]) % M

ans = 0
for i in range(K + 1):
    ans = (ans + nCr(i + S - 1, S - 1) * pow(25, i, M) * pow(26, K - i, M)) % M
print(ans)
