file = open('24.txt')
s = file.readline()
l = 2
k = 0
ans = 10**10
for r in range(2, len(s)):
    if s[r-2:r+1] == 'BAD' or s[r-2:r+1] == 'FAT':
        k += 1
    while k >= 3:
        if s[l-2:l+1] == 'BAD' or s[l-2:l+1] == 'FAT':
            k -= 1
        l += 1
    ans = min(ans, r - l + 1)
print(ans)