#include <bits/stdc++.h>
 
using namespace std;
 
using ll = long long;
using ld = long double;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vi = vector<int>;
 
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define rep(i,a,b) for(int i = (a); i < (b); i++)
 
// g++ -std=c++20 -O2 -Wall template.cpp -o test

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
 
    int n;
    cin >> n;
    string s;
    cin >> s;
    int loBound = INT_MIN;
    int pos = 1;
    vi subsequence;
    rep(i,0,n){
        if(s[i] == '-'){
            subsequence.pb(loBound);
            loBound++;
        } else if(s[i] == '+'){
            subsequence.pb(pos);
            pos++;
        } else subsequence.pb(0);
    }
    vi dp(n);
    rep(k,0,n){
        dp[k] = 1;
        rep(i,0,k){
            if(subsequence[i] < subsequence[k])
                dp[k] = max(dp[k], dp[i]+1);
        }
    }
    cout << *max_element(dp.begin(), dp.end());
}