#include<bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include"debug.h"
#else
#define debug(...) void()
#endif
#define all(x) (x).begin(),(x).end()
template<class T>
auto ary(T *a,int l,int r){
	return vector<T>{a+l,a+1+r};
}
using ll=long long;
using ull=unsigned long long;
using ld=long double;
using LL=__int128;
vector<int>test={2,3,5,7,11,13,17,19,23,29,31,37};
ll mod;
ll qpow(LL x,ll y,ll mod,LL ans=1){
	for(;y;(x*=x)%=mod,y>>=1)if(y&1)(ans*=x)%=mod;
	return ans;
}
bool isprime(ll n){
	if(n<=2)return n==2;
	if(n%2==0)return 0;
	ll a=n-1;
	int k=0;
	for(;a%2==0;a/=2)k++;
	auto chk=[&](int p){
		p%=n;
		if(p==0)return 1;
		ll x=qpow(p,a,n);
		if(x==1)return 1;
		for(int i=0;i<k;i++){
			if(x==n-1)return 1;
			x=(LL)x*x%n;
		}
		return 0;
	};
	for(int x:test)if(!chk(x))return 0;
	return 1;
}
vector<ll>p;
mt19937_64 rnd(time(0));
ll find(ll n){
	ll x=rnd()%(n-2)+1;
	auto f=[&](ll a){
		return ((LL)a*a+x)%n;
	};
	ll a=rnd()%n,b=f(a);
	for(;a!=b;a=f(a),b=f(f(b))){
		ll x=__gcd(abs(a-b),n);
		if(x>1)return x;
	}
	return n;
}
void divide(ll n){
	if(isprime(n))return p.push_back(n);
	ll x;
	do x=find(n);while(x==n);
	divide(x),divide(n/x);
}
ll phi;
bool chk(ll x){
	if(__gcd(x,mod)>1)return 0;
	for(ll y:p){
		if(qpow(x,phi/y,mod)==1)return 0;
	}
	return 1;
}
int main(){
	cin>>mod;
	if(mod==2)puts("1"),exit(0);
	if(mod==4)puts("3"),exit(0);
	divide(mod),sort(all(p));
	if(p[0]==2){
		for(int i=1;i<p.size();i++){
			if(p[i]!=p[1])puts("-1"),exit(0);
		}
		p.erase(p.begin());
		ll x=p.back()-1;
		p.pop_back();
		divide(x);
	}else{
		for(ll x:p){
			if(x!=p.back())puts("-1"),exit(0);
		}
		ll x=p.back()-1;
		p.pop_back();
		divide(x);
	}
	phi=1;
	for(ll x:p)phi*=x;
	sort(all(p)),p.erase(unique(all(p)));
	for(ll g=1;g<mod;g++){
		if(chk(g))printf("%lld\n",g),exit(0);
	}
	puts("-1");
	return 0;
}
#ifdef DEBUG
#include"debug.hpp"
#endif