N = int(input())

T = 'a' * N
print(f'? {T}')
M = int(input())
if M == N:
    print(f'! {T}')
    exit()
Mmx = M

s = 'abcdefghijklmnopqrstuvwxyz'
for i in range(N):
    for j in range(25):
        c = s[j+1]
        T = T[:i] + c + T[i+1:]
        print(f'? {T}')
        M = int(input())
        if M == N:
            print(f'! {T}')
            exit()
        elif M > Mmx:
            Mmx = M
            break
        elif M < Mmx:
            T = T[:i] + 'a' + T[i+1:]
            break

print(f'! {T}')
exit()