#include <stdio.h>
int main(){
	int v[100000],s=0,i,j,t1,t2,t3,t4,n;
	FILE*f=fopen("koba.in","r");
	FILE*g=fopen("koba.out","w");
	fscanf(f,"%d%d%d%d",&n,&t1,&t2,&t3);
	t1%=10;
	t2%=10;
	t3%=10;
	s=(t1%10)+(t2%10)+(t3%10);
	for(i=4;i<=n;i++){
		t4=(t3+((t2%10)*(t1%10)))%10;
		s+=t4%10;
		t1=t2%10;
		t2=t3%10;
		t3=t4%10;
	}
	fprintf(g,"%d",s);
	return 0;
}