#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream gin("cifra.in");
    ofstream gout("cifra.out");
    {
        int n,p,i;
        unsigned long long ucif,s=0,sc;
        gin>>n;
        for(i=1;i<=n;i++)
        {
            p=i;
            ucif=i%10;
            while(p!=1)
            {
                ucif=ucif*i;
                ucif=ucif%10;
                p--;
            }
            s=s+ucif;
            sc=s;
            while (sc>9)
                {
                    s=s%10;
                    sc=sc/10;
                }


        }
        gout<<s;
    }
    return 0;
}