n = int(input())
N = []
S = ""
for i in range(n):
    for j in range(ord('a'), ord('z')):
        c = chr(j)
        print("? " + S + c + 'z' * (n+~i))
        N.append(int(input()))
        if N[-1] == n:
            print("! " + S + c + 'z' * (n+~i))
            exit()
        if len(N) <= 1:
            continue
        elif len(N) == 2 and N[1] < N[0]:
            S += 'a'
            N[1] = N[0]
            break
        elif c == 'a' and N[-1] < N[-2]:
            S += 'z'
            N[-1] = N[-2]
            break
        elif N[-1] > N[-2]:
            S += c
            break
    else:
        S += 'z'
        N[-1] += 1
print("! " + S)