#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<stack>

using namespace std;

#define int long long
#define endl "\n"

const long long INF = (long long)1e18;
const long long MOD = 1'000'000'007; 

string yn(bool f){return f?"Yes":"No";}
string YN(bool f){return f?"YES":"NO";}




signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(10);
	
	int N, con = 0, con91 = 0, con1 = 0, con92;
	bool flag = false;
	string S;
	stack<int> hoge, fuga;
	
	cin>>N;
	cin>>S;
	
	con92 = count(S.begin(), S.end(), '9');
	con1 = count(S.begin(), S.end(), '1');
	
	con += con1/2;
	
	for(int i = 0; i < N; i++){
		if(S[i] == '1'){
			if(con92 >= 1 || con91 >= 2 || (con92 >= 1 && con91 >= 1)) flag = true;
		} else if(S[i] == '9'){
			con91++;
			con92--;
		} else {
			con++;
		}
	}
	cout<<con<<endl;
	
	return 0;
}