import math
A=int(input())
ans=A
for N in range(2,round(math.sqrt(A+2))+1):
    x=round(math.log2(A)/math.log2(N))
    while A<=N**x:x-=1
    x+=1
    if ans>N*x: ans=N*x
    if N>=ans:break

print(ans)