D = int(input())
c0 = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
c1 = input()
c2 = input()
C = c0 + c1 + c2 + c0

from itertools import groupby
def runLengthEncode(S):
    grouped = groupby(S)
    res = []
    for k, v in grouped:
        res.append((k, int(len(list(v)))))
    return res

data = runLengthEncode(C)
M = len(data)

ans = 0
for i in range(M):
    k, v = data[i]
    if k == 'o':
        ans = max(ans, v)
    else:
        pre, nex = 0, 0
        if i != 0:
            pre = data[i - 1][1]
        if i != M - 1:
            nex = data[i + 1][1]
        
        if v <= D: # D 使って両端と接続可能
            sub = pre + v + nex
        else:
            sub = max(pre + D, D + nex)
        
        ans = max(ans, sub)

print(ans)