#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int n;
int messaggio[100000];
int n_mess[100000];

string makeString(int s, int e){
	char p[1];
	string st="";
	for(int i = s; i <= e; i++){
		sprintf(p,"%d",messaggio[i]);
		st = st + p;
	}
	return st;
}

bool confStr(string s){
	bool found = false;
	if(s == "0") found = true;
	if(s == "00") found = true;
	if(s == "001") found = true;
	if(s == "010") found = true;
	if(s == "0010") found = true;
	if(s == "0100") found = true;
	if(s == "0110") found = true;
	return found;
}

void calcolaMessaggi(){
	int lunghezza = 0, cont;
	string subs,ssubs;
	for(int i = (n - 1); i >= 0; i--){
		lunghezza = n - i;
		cont = 0;
		subs = makeString(i,n-1);
		switch(lunghezza){
			case(1):
				subs = makeString(i,n-1);
				if(confStr(subs)) cont = 1;
			break;
			case(2):
				subs = makeString(i,n-1);
				if(confStr(subs)) cont = 1;
				ssubs = makeString(i,i);
				if(confStr(ssubs) && (n_mess[i + 1] != 0)) cont = cont + n_mess[i + 1];
			break;
			case(3):
				subs = makeString(i,n-1);
				if(confStr(subs)) cont = 1;
				for(int j = 0; j < 2; j++){
					ssubs = makeString(i,i + j);
					if(confStr(ssubs) && (n_mess[i + j + 1] != 0)) cont = cont + n_mess[i + j + 1];
				}
			break;
			case(4):
				subs = makeString(i, i+3);
				if(confStr(subs)) cont = 1;
				for(int j = 0; j < 3; j++){
					ssubs = makeString(i,i + j);
					if(confStr(ssubs) && (n_mess[i + j + 1] != 0)) cont = cont + n_mess[i + j + 1];
				}
			break;
			default:
				for(int j = 0; j <= 3; j++){
					ssubs = makeString(i,i + j);
					if(confStr(ssubs) && (n_mess[i + j + 1] != 0)) cont = cont + n_mess[i + j + 1];
				}
			break;
		}
		n_mess[i] = cont;
	}
	ofstream fout("output.txt");
	fout << n_mess[0]%10;
	fout.close();
}

int main() {
	ifstream fin("input.txt");
	fin >> n;
	for(int i = 0; i < n; i++) fin >> messaggio[i];
	fin.close();

	calcolaMessaggi();

  return 0;
}