#!/usr/bin/env python3
n = int(input())
s = input()
s = ''.join(s.split('3'))
s = ''.join(s.split('5'))
s = ''.join(s.split('7'))
ans = n - len(s)
n = len(s)
# dp[checked 0 ~ i][# one][# nine]
dp = [[[-10**5] * 3 for _ in range(3)] for _ in range(n + 1)]
dp[0][0][0] = 0
for i in range(n):
    if s[i] == '1':
        dp[i + 1][1][0] = max(dp[i + 1][1][0], dp[i][0][0])     # '' -> '1'
        dp[i + 1][1][1] = max(dp[i + 1][1][1], dp[i][0][1])     # '' -> '1'
        dp[i + 1][1][2] = max(dp[i + 1][1][2], dp[i][0][2])     # '' -> '1'
        dp[i + 1][0][0] = max(dp[i + 1][0][0], dp[i][1][0] + 1) # '1' -> '11' -> ''
        dp[i + 1][0][1] = max(dp[i + 1][0][1], dp[i][1][1] + 1) # '1' -> '11' -> ''
        dp[i + 1][0][2] = max(dp[i + 1][0][2], dp[i][1][2] + 1) # '1' -> '11' -> ''
        dp[i + 1][0][0] = max(dp[i + 1][0][0], dp[i][0][2] + 1) # '99' -> '991' -> ''
        dp[i + 1][1][0] = max(dp[i + 1][1][0], dp[i][1][2] + 1) # '99' -> '991' -> ''
    else:
        dp[i + 1][0][1] = max(dp[i + 1][0][1], dp[i][0][0])     # '' -> '9'
        dp[i + 1][1][1] = max(dp[i + 1][1][1], dp[i][1][0])     # '' -> '9'
        dp[i + 1][0][2] = max(dp[i + 1][0][2], dp[i][0][1]) # '9' -> '99'
        dp[i + 1][1][2] = max(dp[i + 1][1][2], dp[i][1][1]) # '9' -> '99'
        dp[i + 1][0][0] = max(dp[i + 1][0][0], dp[i][1][0] + 1) # '1' -> '19' -> ''
        dp[i + 1][0][1] = max(dp[i + 1][0][1], dp[i][1][1] + 1) # '1' -> '19' -> ''
        dp[i + 1][0][2] = max(dp[i + 1][0][2], dp[i][1][2] + 1) # '1' -> '19' -> ''
add = 0
for i in range(3):
    for j in range(3):
        add = max(add, dp[n][i][j])
ans += add
print(ans)