#include <bits/stdc++.h> #define PB push_back #define MP make_pair #define REP(i,n) for (int i=0;i<(n);i++) #define FOR(i,a,b) for(int i=(a);i<(b);i++) #define ALL(a) (a).begin(),(a).end() int INF=1e9; int MOD=1000000007; using namespace std; typedef long long ll; typedef unsigned long long ull; double EPS = 1e-10; bool is_prime(long long n){ for(long long i=2;i*i<=n;i++){ if(n%i==0)return false; } return true; } int main(){ long long s; cin>>s; if(s==1){ cout<<1<<endl; return 0; } if(s==4){ cout<<3<<endl; return 0; } if(s==6){ cout<<5<<endl; return 0; } if(s==8||s==9||s==10||s==15||s==16||s==22){ cout<<7<<endl; return 0; } if(s==12){ cout<<11<<endl; return 0; } if(s==14||s==15||s==16){ cout<<13<<endl; return 0; } if(s==20||s==21||s==22){ cout<<19<<endl; return 0; } if(s==24||s==25){ cout<<23<<endl; return 0; } if(s%(long long)8!=1)cout<<8<<endl; else if(!is_prime(s-(long long)8))cout<<8<<endl; else cout<<14<<endl; return 0; }