#include<fstream>   
  
using namespace std;   
  
ifstream fin ("koba.in");   
ofstream fout ("koba.out");   
int main ()   
{   
    int n,i;   
    fin>>n;   
    long long unsigned s;   
    long long unsigned a[n+4];   
    fin>>a[1]>>a[2]>>a[3];   
    s=a[1]%10+a[2]%10+a[3]%10;   
    for(i=3;i<n;i++)   
    {   
    a[i+1]=a[i]+a[i-1]*a[i-2];   
    a[i+1]%=10;   
    s+=a[i+1];   
}//s=0;   
//for(i=1;i<=n;i++)   
//s+=(a[i]%10);   
fout<<s;   
return 0;   
}