mod = 998244353


def main():
    import sys
    input = sys.stdin.readline

    N = int(input())

    dp = [0] * 3
    dp[0] = 1
    ans = 0
    for j in range(N):
        dp_new = [0] * 3
        for i in range(3):
            dp_new[i] = (dp_new[i] + (dp[i] * 25) % mod) % mod
            dp_new[(i + 1) % 3] = (dp_new[(i + 1) % 3] + dp[i]) % mod
            if i == 2:
                ans = (ans + (dp[i] * pow(26, N - j - 1, mod)) % mod) % mod
        dp = dp_new
    print(ans)


if __name__ == '__main__':
    main()