#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000005
#define Inf64 1000000000000000001LL

int main(){
	
	int n;
	cin>>n;
	string s;
	cin>>s;
	vector dp(3,0);
	rep(i,s.size()){
		vector<int> ndp = dp;
		int c;
		if(s[i]=='-')c = 0;
		else if(s[i]=='0')c = 1;
		else c = 2;
		rep(j,3){
			if(j!=c)continue;
			for(int k=j;k<3;k++){
				if(j==1 && k==1)continue;
				ndp[k] = max(ndp[k],dp[j] + 1);
			}
		}
		swap(dp,ndp);
	}
	int ans = 0;
	rep(i,3) ans = max(ans, dp[i]);
	cout<<ans<<endl;
	
	return 0;
}