#include <fstream>
#include <iostream>

typedef unsigned long long int Nr;

short ptrn[10]={0,1,4,4,1,1,4,4,2};

inline short simp(Nr k){
    return k%ptrn[k%10];
}

inline short last(Nr k){
    Nr p=simp(k);
    short d=k%10;
    short c=1;
    while(p){
        c=c*d%10;
        p--;
    }
    return c;
}

int main(){
    Nr n;
    short c=0;
    int t;
    std::ifstream f("cifra.in");
    std::ofstream g("cifra.out");
    f>>n;
    for(Nr i=1;i<=n;i++) c=(c+last(i))%10;
    g<<c<<'\n';
    std::cout<<c<<'\n';
    g.close();f.close();return 0;
}