#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
//#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
//#include<list>
#include<queue>
#include<deque>
#include<algorithm>
//#include<numeric>
#include<utility>
#include<complex>
//#include<memory>
#include<functional>
#include<cassert>
#include<set>
#include<stack>

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
//typedef long long ll;
typedef __int128 ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;

const int MAXN = 100;
bool prime[MAXN];
bool done[MAXN][MAXN];

ll pow_mod(ll a, ll p, ll mod) {
    if (a == 0) return 0;
    if (p == 0) return 1;
    if (p == 1) return a;
    if (p%2) return a*pow_mod(a, p-1, mod)%mod;
    ll tmp = pow_mod(a, p/2, mod);
    return tmp*tmp&mod;
}

bool check(ll a, ll n, int k, ll q) {
    ll tmp = pow_mod(a, q, n);
    if (tmp == 1) return true;
    for (int i = 0; i < k-1; i++) {
        tmp = tmp*tmp%n;
        if (tmp == n-1) return true;
        if (tmp == 1) return false;
    }
    return false;
}

bool isPrime(ll n) {
    ll q = n-1;
    int k = 0;
    while (q%2==0) {
        q /= 2;
        k++;
    }
    vector<ll> p = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41};
    for (ll a : p) {
        if (!check(a, n, k, q)) return false;
    }
    return true;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    for (int i = 2; i < MAXN; i++) prime[i] = true;
    for (int i = 2; i < MAXN; i++) {
        if (prime[i]) for (int j = 2; j*i < MAXN; j++) prime[i*j] = false;
    }
    string s;
    cin >> s;
    ll N = 0;
    reverse(s.begin(), s.end());
    for (char el : s) N = N*10+(el-'0');
    if (N < 100) {
        for (int w = 2; w < N; w++) {
            int h = N/w+(N%w!=0);
            vector<vi> board(h, vi(w));
            for (int j = 0; j < N; j++) {
                board[j/w][j%w] = j+1;
            }
            assert(board[(N-1)/w][(N-1)%w] == N);
            queue<pii> que;
            memset(done, false, sizeof(done));
            que.push(pii(0, 0));
            done[0][0] = true;
            while (!que.empty()) {
                pii p = que.front(); que.pop();
                for (int k = 0; k < 4; k++) {
                    int ny = p.first+dy[k];
                    int nx = p.second+dx[k];
                    if (ny < 0 || ny >= h || nx < 0 || nx >= w || board[ny][nx] == 0 || prime[board[ny][nx]]) continue;
                    if (done[ny][nx]) continue;
                    done[ny][nx] = true;
                    que.push(pii(ny, nx));
                }
            }
            if (done[(N-1)/w][(N-1)%w]) {
                cout << w << endl;
                return 0;
            }
        }
    } else {
        if (N%8 == 1 && isPrime(N-8)) cout << 14 << endl;
        else cout << 8 << endl;
    }
    return 0;
}