#include<stdio.h>

int main()
{
    freopen("koba.in","r",stdin);
    freopen("koba.out","w",stdout);
    int n,a,b,c,d,i,aux;
    long long s=0;
    scanf("%d%d%d%d",&n,&a,&b,&c);
    a%=10;
    b%=10;
    c%=10;
    s=a+b+c;
    for(i=4;i<=n;++i)
    {
        aux=(c+a*b)%10;
        a=b;b=c;c=aux;
        s+=aux;
    }

    printf("%lld\n",s);
    return 0;
}