#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef __int128_t i128;
ll n,ph;
ll FP(ll bs,ll k){
	i128 ret = 1, mul = bs;
	while(k){
		if(k&1ll) ret = ret*mul%n;
		mul = mul*mul%n;
		k >>= 1;
	}
	return (ll)ret;
}
bool chk(ll x){
	if(!(x%4)) return 0;
	if(!(x%2)) x/=2;
	for(int al=2;(ll)al*al<=x;al++)if(!(x%al)){
		while(!(x%al)) x/=al;
		if(x!=1) return 0;
		return 1;
	}
	return 1;
}
bool calc(ll x){
	ll ph_ = ph;
	for(int al=2;(ll)al*al<=ph_;al++)if(!(ph_%al)){
		if(FP(x,ph/al)==1) return 0;
		while(!(ph_%al)) ph_ /= al;
	}
	return 1;
}
int main(){
	scanf("%lld",&n);
	if(n==2) printf("1\n");
	else if(n==4) printf("3\n");
	else if(!chk(n)) printf("-1\n");
	else{
		ph = n; ll cur = n;
		for(int al=2;(ll)al*al<=cur;al++)if(!(cur%al)){
			ph /= al, ph *= (al-1);
			while(!(cur%al)) cur /= al;
		}
		if(cur!=1) ph /= cur, ph *= (cur-1);
//		system("pause");
		for(int al=2;;al++)if(calc(al)){printf("%d\n",al); break;}
	}
	return 0;
}