#include<stdio.h>
long long t1,t2,t3;
long long n;
int main()
{ freopen("koba.in","r",stdin);
  freopen("koba.out","w",stdout);
  scanf("%lld%d%d%d",&n,&t1,&t2,&t3);
  long long i,suma=0,t4;
  suma=t1%10+t2%10+t3%10;
  for(i=4;i<=n;i++)
     { t4=t3%10+(t2%10)*(t1%10);
       suma+=t4%10;
       t1=t2;
       t2=t3;
       t3=t4%10;
     }
  printf("%lld\n",suma);
  return 0;
}