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

int main()
{
ifstream f("cifra.in");
ofstream g("cifra.out");    

int i,t,s=0,j,put;
f>>t;
for(i=1; i<=t; i++)
    {
    put = i%10;
    for(j=1; j<i; j++)    // ridicare la putere pe parcurs
       {
        put = (put * i%10)%10;
       }    
    s = (s + put)%10;     // adunare put
    }    
g<<s;

f.close();
g.close();
}