#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 vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;

const int MAXN = 1000;
bool prime[MAXN];
bool done[MAXN][MAXN];

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;
    if (s.size() > 3) {
        cout << 8 << endl;
        return 0;
    }
    int N = stoi(s);
    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;
        }
        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;
        }
    }
    return 0;
}