#include <stdio.h>
long s,a,b,c,d,n,i;
int main(){
	FILE *f,*g;
	f=fopen("koba.in","r");
	g=fopen("koba.out","w");
	fscanf(f,"%ld%ld%ld%ld",&n,&a,&b,&c);
	n-=3;
	a%=10;b%=10;c%=10;
	long s=a+b+c;
	for(i=1;i<=n;i++){
		d=(a+(b*c)%10)%10;
		s+=d;
		a=b;
		b=c;
		c=d;
	}
	fprintf(g,"%ld\n",s);
	fclose(f);
	fclose(g);
	return 0;
}