#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

void findPrime(int N, vector<bool>& isPrime)
{
    isPrime.assign(N+1, true);
    isPrime[0] = isPrime[1] = false;
    for(int i=2; i*i<=N; i++){
        if(isPrime[i]){
            for(int j=i; i*j<=N; j++){
                isPrime[i*j] = false;
            }
        }
    }
}

int main()
{
    int n;
    cin >> n;

    if(n > 100){
        cout << 8 << endl;
        return 0;
    }

    vector<bool> isPrime;
    findPrime(n, isPrime);

    for(int w=2; ; ++w){
        const int d[] = {-1, 1, -w, w};
        vector<bool> check(n+1, false);
        queue<int> q;
        check[1] = true;
        q.push(1);

        while(!q.empty()){
            int a = q.front();
            q.pop();

            for(int i=0; i<4; ++i){
                int b = a + d[i];
                if(!(1 <= b && b <= n) || (a % w != b % w && a / w != b / w))
                    continue;
                if(!isPrime[b] && !check[b]){
                    check[b] = true;
                    q.push(b);
                }
            }
        }
        if(check[n]){
            cout << w << endl;
            return 0;
        }
    }
}