// ,,廿_廿,,
#include<iostream>
#include<vector>
using namespace std;


int main(){
	int n;cin>>n;
	vector<int> a(n);
	string s;cin>>s;
	int mi = -(1<<25);
	int pv = 1;
	for(int i=0;i<n;++i){
		if(s[i] == '+')a[i]=pv++;
		else if(s[i] == '-')a[i]=mi++;
		else a[i] = 0;
	}

	int inf = 1<<25;
	vector<int> dp(n+1,inf);
	for(int i=0;i<n;++i){
		int t = a[i];
		auto id = lower_bound(begin(dp),end(dp),t) - begin(dp);
		if(t < dp[id])dp[id] = t;
	}

	cout << 
		lower_bound(begin(dp),end(dp),inf) - begin(dp) << endl;
	

}