---

s = open('1.txt').read()
m = 0

for l in range(len(s)):
    for r in range(l + m, len(s)):
        c = s[l:r+1]
        if 'G' in c or 'W' in c or 'P' in c:
            break
        else:
            m = max(len(c), m)
    
    if l % 100_000 == 0:
        print(l, r, m)

print(m)