#include<stdio.h>

long n, i, s=0;
int t1, t2, t3, aux;

void citire()
{
     freopen("koba.in","r",stdin);
     scanf("%ld %d %d %d", &n, &t1, &t2, &t3);
     fclose(stdin);
}

void afisare()
{
     freopen("koba.out","w",stdout);
     printf("%ld\n",s);
     fclose(stdout);
}

int main()
{
    citire();
    s=(t1+t2+t3)%10;
    t1%=10; t2%=10; t3%=10;
    for(i=4; i<=n; i++){
	     aux=(t3+t2*t1)%10;
             s+=aux;
             t1=t2; t2=t3; t3=aux;
             }
    afisare();
    return 0;
}