#include <bits/stdc++.h>
using namespace std;
using ui = unsigned;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
#define rep(i,l,r) for(int i=(l);i<=(r);++i)
#define per(i,l,r) for(int i=(l);i>=(r);--i)
#define repn(i,n)  for(int i=0;i<(n);++i)
#define sizc(x) ((int)x.size())
#define allc(x) x.begin(),x.end()
#define fir first
#define sec second
namespace KnownError_{
    mt19937_64 rng(random_device{}());
    ll n,phi;
    ll getphi(ll n){
        ll res=n;
        for(ll i=2;i*i<=n;++i)if(n%i==0){
            res=res/i*(i-1);
            while(n%i==0)n/=i;
        }
        if(n>1)res=res/n*(n-1);
        return res;
    }
    vector<ll> factorize(ll n){
        vector<ll> res;
        for(ll i=2;i*i<=n;++i)if(n%i==0){
            res.push_back(i);
            while(n%i==0)n/=i;
        }
        if(n>1)res.push_back(n);
        return res;
    }
    vector<ll> fac;
    ll qpow(ll x,ll y){
        ll ret=1;
        while(y){
            if(y&1)ret=(__int128_t)ret*x%n;
            x=(__int128_t)x*x%n;
            y>>=1;
        }
        return ret;
    }
    bool check(ll x){
        if(__gcd(x,n)>1)return 0;
        for(auto p:fac)if(qpow(x,phi/p)==1)return 0;
        return 1;
    }
    void main(){
        cin>>n;
        if(n==1){cout<<"-1\n";return;}
        if(n==2){cout<<"1\n";return;}
        fac=factorize(phi=getphi(n));
        while(clock()<0.9*CLOCKS_PER_SEC){
            ll x=rng()%n;
            if(check(x)){cout<<x<<'\n';return;}
        }
        cout<<"-1\n";
    }
}
signed main(){
    // freopen(".in","r",stdin);
    // freopen(".out","w",stdout);
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    KnownError_::main();
}