n = int(input())
s = input()
if 'H' in s:
    print(-1)
    exit()
#[0, r)
cnt = 0
for r in range(1, n + 1):
    cnt += s[r-1] == 'Q'
    if cnt * r == n:
        code = s[:r]
        if code * cnt == s:
            print(code)
            exit()
print(-1)