/*

#include <iostream>
#include <fstream>
using namespace std;

long long LogPow(long long x,long long n)
{
    long long p=1;
    while(n>0)
    {
        if(n%2!=0)
        {
            p=p*x%10;
            n--;
        }
        x=x*x%10;
        n=n/2;
    }
    return p;
}

int main()
{
    ifstream in("cifra.in");
    ofstream out("cifra.out");
    long long s=0,a;
    long long n;
     in >> n;
    for(int j=0;j<n;j++)                //while(!in.eof())
    {
        in >> a;
        s=0;
        for(int i=1;i<=a;i++)
        {
            s=s+LogPow(i,i)%10;
        }
        out << s%10 << "\n";
    }

    return 0;
}

*/

#include <iostream>
#include <fstream>
using namespace std;

long long n,p,i,S;
long long tip;
long long put(long n, long p)
{
 if(p==0) return 1;
 if(p%2==1)
 return (n*put(n,p-1))%10;
 tip=put(n,p/2)%10;
 return tip*tip%10;
}

int main()
{
 ifstream f("ucif.in");
 ofstream g("ucif.out");
 f>>n;
 f.close();
 for(i=1;i<=n;++i)
 {
 p=i;
 S+=put(i,p);
 }
 g<<S%10;
 g.close();
 return 0;
}