#include<bits/stdc++.h>
using namespace std;
long long q,logsum[100]={0,1,8,343,1331,1030301,1367631,1003003001,10662526601,1000300030001,1030607060301,1334996994331,1000030000300001,1033394994933301,133139931331,1000000000000000000},n;
long long check(long long l,long long r){
	long long mid=(l+r)/2+1;
	if(l==r){
		cout<<logsum[l]<<endl;
		return 0;
	}
	if(logsum[mid]<=n){
		return check(mid,r);
	}
	else{
		return check(l,mid-1);
	}
}
int main(){
	cin>>n;
	check(1,15);
	return 0;
}