ABC215 E - Chain Contestant

MOD = 998244353
MAX_S = 10
 
n = int(input())
s = list(map(lambda x: ord(x) - ord('A'), input()))
 
# dp[i][j][k] := s[:i]までで、利用した文字集合がj、最後の文字がkの場合の数
dp = [[[0] * (MAX_S + 1) for _ in range(1 << MAX_S)] for _ in range(n + 1)]
dp[0][0][10] = 1
 
for i in range(n):
    for j in range(1 << MAX_S):
        for k in range(MAX_S + 1):
            if True:  # s[i]を選択しない
                dp[i + 1][j][k] += dp[i][j][k]
                dp[i + 1][j][k] %= MOD
            if not 1 << s[i] & j:  # s[i]を初選択
                dp[i + 1][j | 1 << s[i]][s[i]] += dp[i][j][k]
                dp[i + 1][j | 1 << s[i]][s[i]] %= MOD
            if 1 << s[i] & j and s[i] == k:  # s[i]を連続で選択
                dp[i + 1][j][s[i]] += dp[i][j][k]
                dp[i + 1][j][s[i]] %= MOD
 
# print(*dp, sep='\n')
 
ans = 0
for j in range(1 << MAX_S):
    for k in range(MAX_S):
        ans += dp[n][j][k]
        ans %= MOD
 
print(ans)