#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i,n) for (int i = 0; i < (n); i++)
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define all(v) begin(v),end(v)
#define fi first
#define se second
template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
constexpr ll inf = 2e9;
constexpr ll llinf = 9e18;
//constexpr ll mod = 998244353;
constexpr ll mod = 1000000007;
const double pai=acos(-1);

int main() {
    //cout<<fixed<<setprecision(15);
    ll n;cin>>n;
    REP(i,2,sqrt(n)+1){
        ll x=n;
        string s;
        bool ok=false;
        while(x){
            if(x%i>=10){
                ok=true;
                break;
            }
            s+=to_string(x%i);
            x/=i;
        }
        if(ok)break;
        bool ok2=true;
        rep(j,s.size()-1){
            if(s[j]!=s[j+1])ok2=false;
        }
        if(ok2){
            cout<<i<<endl;
            return 0;
        }
    }
    cout<<n-1<<endl;
}