n = int(input())
s = input()
if set(s) & {'+', 'Q'} != set(s):
    print(-1)
    exit()
#[x, r)
cnt = 0
for r in range(1, n + 1):
    cnt += s[r-1] == 'Q'
    if cnt * r == n:
        code = s[:r]
        break
else:
    print(-1)
    exit()
if code * cnt == s:
    print(code)
else:
    print(-1)