#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll inf=14449999999999999;
ll mod=998244353;
ll modpow(ll x, ll n) {
  if(n==0) return 1;  //再帰の終了条件

  else if(n%2==1) {
    return (x*modpow(x, n-1));  //nが奇数ならnを1ずらす
  }
  else return modpow((x*x), n/2);  //nが偶数ならnが半分になる
}
int main(){
    ll n;
    cin >> n;
    if (n==1)
    {
        cout << 2 << endl;
        return 0;
    }else if (n==2)
    {
        cout << 3 << endl;
        return 0;
    }
    ll ans=n-1;
    vector<ll>y(2000000,1);
    for (ll i = 2; i*i <=n; i++)
    {
        if (n%i==0&&n/i-1>i)
        {
            ans=n/i-1;
        }
    }
    
    for (ll i = 1; i <=43; i++)
    {
        for (ll j = 2; j <=ans; j++)
        {
            if (j>=y.size())
            {
                break;
            }
            y[j]*=j;
            y[j]+=1;
            if (y[j]>n)
            {
                break;
            }
            if (n%y[j]==0&&n/y[j]<j)
            {
                ans=j;
                break;
            }
        }
    }
    cout << ans << endl;
}