#include<bits/stdc++.h>
using namespace std;
namespace my_std{
	#define ll long long
	#define bl bool
	ll my_pow(ll a,ll b,ll mod){
		ll res=1;
		if(!b) return 1;
		while(b){
			if(b&1) res=(res*a)%mod;
			a=(a*a)%mod;
			b>>=1;
		}
		return res;
	}
	ll qpow(ll a,ll b){
		ll res=1;
		if(!b) return 1;
		while(b){
			if(b&1) res*=a;
			a*=a;
			b>>=1;
		}
		return res;
	}
	#define db __float128
	#define pf printf
	#define pc putchar
	#define fr(i,x,y) for(register ll i=(x);i<=(y);i++)
	#define pfr(i,x,y) for(register ll i=(x);i>=(y);i--)
	#define go(u) for(ll i=head[u];i;i=e[i].nxt)
	#define enter pc('\n')
	#define space pc(' ')
	#define fir first
	#define sec second
	#define MP make_pair
	#define il inline
	#define inf 1e18
	#define random(x) rand()*rand()%(x)
	#define inv(a,mod) my_pow((a),(mod-2),(mod))
	il ll read(){
		ll sum=0,f=1;
		char ch=0;
		while(!isdigit(ch)){
			if(ch=='-') f=-1;
			ch=getchar();
		}
		while(isdigit(ch)){
			sum=sum*10+(ch^48);
			ch=getchar();
		}
		return sum*f;
	}
	il void write(ll x){
		if(x<0){
			x=-x;
			pc('-');
		}
		if(x>9) write(x/10);
		pc(x%10+'0');
	}
	il void writeln(ll x){
		write(x);
		enter;
	}
	il void writesp(ll x){
		write(x);
		space;
	}
}
using namespace my_std;
mt19937 rd(114514);
vector<ll> fac;
ll n,pri[1000010],cnt=0,phi;
bl ck[1000010];
il void init(ll N){
	fr(i,2,N){
		if(!ck[i]) pri[++cnt]=i;
		fr(j,1,cnt){
			if(i*pri[j]>N) break;
			ck[i*pri[j]]=1;
			if(i%pri[j]==0) break;
		}
	}
}
il ll mpow(ll x,ll y,ll mod){
	ll res=1;
	while(y){
		if(y&1) res=(__int128)res*x%mod;
		x=(__int128)x*x%mod;
		y>>=1;
	}
	return res;
}
il bl mr(ll N){
	if(N==2||N==3) return 1;
	if(N%2==0||N==1) return 0;
	ll tmp=N-1,k=0;
	while(tmp%2==0){
		tmp>>=1;
		k++;
	}
	fr(i,1,12){
		if(N==pri[i]) return 1;
		ll x=mpow(pri[i],tmp,N),nxt;
		fr(j,1,k){
			nxt=(__int128)x*x%N;
			if(nxt==1&&x!=1&&x!=(N-1)) return 0;
			x=nxt;
		}
		if(x!=1) return 0;
	}
	return 1;
}
il bl chk(){
	if(n==2){
		phi=1;
		return 1;
	}
	if(n==4){
		phi=2;
		return 1;
	}
	fr(i,2,cnt){
		ll tmp=n;
		while(tmp%pri[i]==0) tmp/=pri[i];
		if(tmp==1){
			phi=n/pri[i]*(pri[i]-1);
			return 1;
		}
		if(n&1) continue;
		tmp=n/2;
		while(tmp%pri[i]==0) tmp/=pri[i];
		if(tmp==1){
			phi=n/2/pri[i]*(pri[i]-1);
			return 1;
		}
	}
	if(n<=1000000) return 0;
	if(mr(n)){
		phi=n-1;
		return 1;
	}
	if(n%2==0&&mr(n/2)){
		phi=n/2-1;
		return 1;
	}
	ll tmp=sqrt(n);
	if(tmp*tmp==n&&mr(tmp)){
		phi=n/tmp*(tmp-1);
		return 1;
	}
	if(n%2==0){
		tmp=sqrt(n/2);
		if(2*tmp*tmp==n){
			phi=n/2/tmp*(tmp-1);
			return 1;
		}
	}
	return 0;
}
il ll PR(ll x){
	ll s=0,t=0,len=1,c=rd()%(x-1)+1,mul=1;
	while(1){
		fr(i,1,len){
			t=((__int128)t*t+c)%x;
			mul=(__int128)mul*abs(t-s)%x;
			if(i%127==0){
				ll d=__gcd(mul,x);
				if(d>1) return d;
			}
		}
		ll d=__gcd(mul,x);
		if(d>1) return d;
		s=t;
		len<<=1;
	}
}
il void solve(ll x){
	if(x==1) return;
	if(mr(x)){
		fac.push_back(x);
		return;
	}
	ll d=PR(x);
	while(d==x) d=PR(x);
	solve(d);
	solve(x/d);
}
int main(){
	n=read();
	if(n==1){
		write(-1);
		return 0;
	}
	init(1000000);
	if(!chk()){
		write(-1);
		return 0;
	}
	solve(phi);
	sort(fac.begin(),fac.end());
	fac.erase(unique(fac.begin(),fac.end()),fac.end());
	ll g=1;
	while(1){
		if(__gcd(g,n)>1){
			g++;
			continue;
		}
		bl pd=0;
		fr(i,0,(ll)fac.size()-1){
			if(mpow(g,phi/fac[i],n)==1){
				pd=1;
				break;
			}
		}
		if(!pd){
			write(g);
			return 0;
		}
		g++;
	}
}