#include<stdio.h>
#include<stdlib.h>
long n;
int v[100002];


void citeste()
{int  t;
FILE *f=freopen("koba.in","r",stdin);
fscanf(f,"%l",&n);
fscanf(f,"%d",&t);
v[1]=t%10;
fscanf(f,"%d",&t);
v[2]=t%10;
fscanf(f,"%d",&t);
v[3]=t%10;
fclose(f);};

void genereaza(){long i;
     for(i=4;i<=n;i++)v[i]=(v[i-3]+(v[i-2]*v[i-1])%10)%10;
     }

void aduna_scrie(){
     long s=0;long i;
     for(i=1;i<=n;i++)s+=v[i];
     FILE *o=freopen("koba.out","w",stdout);
     fprintf(o,"%l\n",s);
     fclose(o);
     }

int main(int argc,char *argv[])
{citeste();
genereaza();
aduna_scrie();
return 0;}