#include<stdio.h>
FILE *fin=fopen("koba.in","r");
FILE *fout=fopen("koba.out","w");

int n,v[6],s,i;

int main(){
	
	fscanf(fin,"%d %d %d %d",&n,&v[1],&v[2],&v[3]);
	v[1]%=10; 
	v[2]%=10;
	v[3]%=10;
	n-=3;
	s=v[1]+v[2]+v[3];
	
	for(i=1;i<=n;i++){
		v[4] = ( v[3]+v[2]*v[1] )%10;
		s+=v[4];
		
		v[1] = v[2];
		v[2] = v[3];
		v[3] = v[4];
	}
	
	fprintf(fout,"%d",s);
	
	return 0;
}