ok=1
ng=1000
t=0
while t<25:
    middle=(ok+ng)//2
    print("?",middle)
    t+=1
    if input()=="safe":
        ok=middle
        continue
    else:
        print("?",middle-1)
        t+=1
        if input()=="out":
            ng=middle-1
        else:
            ok=middle-1
print("!",ok)