#include <iostream>

using namespace std;

int main()
{
    int n; cin >> n; // 1620

    while(n >= 10)
    {
        int a[6] = {0};
        int cnt = 1, sum = 1;

        while(n > 0)
        {
            a[cnt] = n % 10;
            n /= 10;
            cnt++;
        }

        for(int i = 1; i <= 6; i++)
        {
            if(a[i] != 0)
            {
                sum *= a[i];
            }
        }

        n = sum;
    }

    cout << n << endl;

    return 0;
}