#include<fstream>
using namespace std;
ifstream fin("ucif.in");
ofstream fout("ucif.out");
int log(int x,int n)
{
 if(n==0) return 1;
 if(n%2==0) return log(x,n/2)*log(x,n/2)%10;
 if(n%2==1) return x*log(x,n-1)%10;
}

int main()
{
    int n,S=0;
    fin>>n;
    for(int i=1;i<=n;i++) S+=log(i,i) ;
    fout<<S%10;
    fin.close();
    fout.close();
    return 0;
}