#include <stdio.h>

long long int n;

int sum;
long long int v[100000000];

int main() {
int i;
scanf("%lld",&n);

scanf("%d",&v[1]);

scanf("%d",&v[2]);

scanf("%d",&v[3]);

sum = v[1]%10 + v[2]%10 + v[3]%10;

for (i=4; i<=n; i++) {
   v[i] = v[i-1] + (v[i-2]*v[i-3]);
   sum+=v[i]%10;
}
printf("%d",sum);



      system("PAUSE");
      return 0;
}