#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;

//template
#define rep(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define ALL(v) (v).begin(),(v).end()
typedef long long int ll;
const int inf = 0x3fffffff; const ll INF = 0x1fffffffffffffff; const double eps=1e-12;
template<typename T>inline bool chmax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
template<typename T>inline bool chmin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
//end



int main(){
   ll n; cin>>n;
   for(ll p=2;p*p<=n;p++){
      ll m=n; ll v=m%p;
      for(;m;m/=p){
         if(m%p!=v)goto fail;
      }
      cout<<p<<endl;
      return 0;
      fail:;
   }
   vector<ll> ds;
   for(ll d=1;d*d<=n;d++)if(n%d==0){
      ds.push_back(d);
      if(d*d!=n)ds.push_back(n/d);
   }
   sort(ALL(ds));
   for(auto& d:ds)if(d>=3 and n/d<d-1){
      cout<<d-1<<endl;
      return 0;
   }
   return 0;
}