import sys
input = sys.stdin.readline

C=int(input())

OK=10**5
NG=-10**5

for i in range(60):
    mid=(OK+NG)/2

    if mid**5+mid-C>=0:
        OK=mid
    else:
        NG=mid

k=int(OK*1000)

for i in range(k-10,k+10):
    x=i/1000
    if x**5+x-C>0:
        print((i-1)/1000)
        break