MOD = 998244353

N, K = map(int, input().split())
S = ['P'] + list(input())

max_plan = S.count('N') - K

# dp[i][j]: i日目までに予定をj個入れる入れ方
dp = [[0]*(max_plan + 1) for _ in range(N+1)]
dp[0][0] = 1

for i in range(1, N+1):
    if S[i] != 'N' or S[i-1] == 'C':
        for j in range(max_plan + 1):
            dp[i][j] = dp[i-1][j]
        continue
    
    dp[i][0] = dp[i-1][0]
    for j in range(1, max_plan + 1):
        dp[i][j] += dp[i-1][j]
        dp[i][j] += dp[i-1][j-1]

print(sum(dp[N][j] for j in range(1, max_plan + 1)))