#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin >> n;
    for (int i=n-1;i>=2;i--)
    {
        int p=i,flag=0;
        for (int j=2;j<p;j++)
        {
            if (p%j == 0)
            {
                flag=1;
                break;
            }
        }
        if (flag == 0)
        {
            cout << i << endl;
            break;
        }
    }
    return 0;
}