from collections import defaultdict

N=int(input())
ans=["a"]*N
d=defaultdict(int)

d["b"]=1
  
for i in range(N):
  
  t="".join(ans)
  print("?",t,flush=1)
  x=int(input())
  for j in range(1,26):
    if d[chr(97+j)]==0:
      continue
    ans[i]=chr(97+j)
    t="".join(ans)
    print("?",t,flush=1)
    n=int(input())
    if n>x:
      d[chr(97+j)]-=1
      break
print("!","".join(ans))