#include<bits/stdc++.h>
#define ull unsigned long long
#define ui unsigned int
#define ld long double
#define ll long long
#define lll __int128
#define fi first
#define se second
#define e emplace
#define eb emplace_back
#define db double
#define ef emplace_front
#define pii pair<int,int>
#define pll pair<ll,ll>
#define vi vector<int>
#define vp vector<pii>
#define mp make_pair

//#define LOCALJUDGE
 #define int __int128
bool ST;
static const ll MOD=998244353,Phi=998244352,inv2=499122177,Root=3,iRoot=332748118;
static const ll inf=1073741823,INF=4557430888798830399;
static const ld eps=1e-9,pi=3.1415926535;
char in[1<<20],*p1=in,*p2=in;
using namespace std;
//#define getchar() (p1==p2&&(p2=(p1=in)+fread(in,1,1<<20,stdin),p1==p2)?EOF:*p1++)
struct tup{int x,y,z;tup(int X=0,int Y=0,int Z=0){x=X,y=Y,z=Z;}};
namespace FastIO
{
	template<typename T> inline void write(T x,char ch=' ')
	{
		if(is_same<char,T>::value)putchar(x);
		else
		{
			if(x<0)x=-x,putchar('-');
			static char st[25];int top=0;
			do{st[top++]=x%10+'0',x/=10;}while(x);
			while(top)putchar(st[--top]);
		}
		ch!='~'?putchar(ch):0;
	}
	inline void write(const char*x,char ch=' ')
	{
		for(int i=0;x[i]!='\0';++i)putchar(x[i]);
		ch!='~'?putchar(ch):0;
	}
	inline void read(char&s){do s=getchar();while(s=='\n'||s==' ');}
	inline void read(char s[])
	{
		int len=0;char st;
		do st=getchar();while(st=='\n'||st==' ');
		s[++len]=st,st=getchar();
		while(st!='\n'&&st!=' ')s[++len]=st,st=getchar();
		s[++len]='\0';
	}
	template<typename T> inline void read(T &s)
	{
		
		s=0;char ch=getchar();
		while((ch>'9'||ch<'0')&&ch!='-')ch=getchar();
		bool tf=(ch=='-')&&(ch=getchar());
		while((ch>='0')&&(ch<='9'))s=(s<<1)+(s<<3)+ch-'0',ch=getchar();
		s=(tf?-s:s);
	}
	template<typename T1,typename T2> inline void read(pair<T1,T2> &s){read(s.fi),read(s.se);}
	template<typename T,typename...Args> inline void write(T x,Args...args){write(x,'~'),write(args...);}
	template<typename T,typename...Args> inline void read(T&x,Args&...args){read(x),read(args...);}
}	
using namespace FastIO;
namespace MTool
{
	inline int Cadd(int a,int b){return (ll)a+b>=MOD?(ll)a+b-MOD:a+b;}
	inline int Cdel(int a,int b){return a-b<0?a-b+MOD:a-b;}
	inline int Cmul(int a,int b){return 1ll*a*b%MOD;}
	inline int sqr(int a){return 1ll*a*a%MOD;}
	inline void Madd(int&a,int b){a=((ll)a+b>=MOD?(ll)a+b-MOD:a+b);}
	inline void Mdel(int&a,int b){a=(a-b<0?a-b+MOD:a-b);}
	inline void Mmul(int&a,int b){a=1ll*a*b%MOD;}
	template<typename T> inline bool Mmax(T&a,T b){return a<b?a=b,1:0;}
	template<typename T> inline bool Mmin(T&a,T b){return a>b?a=b,1:0;}
	template<typename...Args> inline void Madd(int&a,int b,Args...args){Madd(a,b),Madd(a,args...);}
	template<typename...Args> inline void Mmul(int&a,int b,Args...args){Mmul(a,b),Mmul(a,args...);}
	template<typename...Args> inline void Mdel(int&a,int b,Args...args){Mdel(a,b),Mdel(a,args...);}
	template<typename...Args> inline int Cadd(int a,int b,Args...args){return Cadd(Cadd(a,b),args...);}
	template<typename...Args> inline int Cmul(int a,int b,Args...args){return Cmul(Cmul(a,b),args...);}
	template<typename...Args> inline int Cdel(int a,int b,Args...args){return Cdel(Cdel(a,b),args...);}
	template<typename...Args,typename T> inline bool Mmax(T&a,T b,Args...args){return Mmax(a,b)|Mmax(a,args...);}
	template<typename...Args,typename T> inline bool Mmin(T&a,T b,Args...args){return Mmin(a,b)|Mmin(a,args...);}
//	inline int power(int x,int y){int s=1;for(;y;y>>=1,Mmul(x,x))if(y&1)Mmul(s,x);return s;}
}
using namespace MTool;
namespace WrongAnswer_90
{
	int n;
	inline int power(int x,int y,int z)
	{
		int s=1;
		for(;y;y>>=1,x=(__int128)x*x%z)if(y&1)s=(__int128)s*x%z;
		return s;
	}
	int phi(int x)
	{
		int s=1;
		for(int i=2;i*i<=x;++i)
		{
			if(x%i==0)
			{
				s*=i-1,x/=i;
				while(x%i==0)s*=i,x/=i;
			}
		}
		if(x!=1)s*=x-1;
		return s;
	}
	vi ve;
	inline void mian()
	{
		read(n);int nn=n;
		if(n==2)return write(1);
		if(n==4)return write(3);
//		assert(n!=1); 
		if(n==1)return write(-1);
		if(n%4==0)return write(-1);
		if(n%2==0)nn/=2;
		for(int i=3;i*i<=nn;++i)
		{
			if(nn%i==0)
			{
				while(nn%i==0)nn/=i;
				if(nn!=1)return write(-1);
			}
		}
		int m=phi(n),mm=m;
		for(int i=2;i*i<=m;++i)
		{
			if(m%i==0)ve.eb(i);
			while(m%i==0)m/=i;
		}
		if(m>1)ve.eb(m);
		m=mm;
		for(int i=2;;++i)
		{
			int fl=1;
			if(__gcd(i,n)!=1)continue;
			for(auto p:ve)fl&=power(i,m/p,n)!=1;
			if(fl)return write(i);
		}
		assert(0);
	}
}
bool ED;
signed main()
{
//	#ifdef LOCALJUDGE
//	freopen("1.in","r",stdin);
//	freopen("1.out","w",stdout);
//	#endif
	double st=clock();
	WrongAnswer_90::mian();
	double ed=clock();
	#ifndef LOCALJUDGE
 	cerr<<endl;
	#endif
 	cerr<<"Time: "<<ed-st<<" ms\n";
	#ifdef LOCALJUDGE
 	cerr<<"     ";
	#endif
 	cerr<<"Memory: "<<abs(&ST-&ED)/1024.0/1024.0<<" MB\n";
	return 0;
}