#include<stdio.h>

#define INPUT "koba.in"
#define OUTPUT "koba.out"
#define DIM 100000001

void Rezolvare();
long long unsigned n,suma,produs,S,a[DIM];

int main()
{
    freopen(INPUT,"r",stdin);
    freopen(OUTPUT,"w",stdout);
    Rezolvare();
    return 0;
}
void Rezolvare()
{
     int i;
     scanf("%llu%llu%llu%llu",&n,&a[1],&a[2],&a[3]);
     S=(a[1]%10)+(a[2]%10)+(a[3]%10);
     for(i=3; i<n-1; ++i)
     {
              a[i]=a[i-1]+a[i-2]*a[i-3];
              S+=a[i]%10;
     }
     printf("%llu",S);
}