#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 check(vi LIS, vi subsequence, int i, int n, int debug){
    vi curr;
    int maxSize = LIS.size();
    rep(j, i+1, n){
        curr = LIS;
        if(curr.back() < subsequence[j]){
            curr.pb(subsequence[j]);
            int currSize = curr.size();
            maxSize = max(maxSize, max(currSize, check(curr, subsequence, j, n, debug+1)));
        }
    }
    return maxSize;
}

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);
    }
    int maxSize = 1;
    rep(i,0,n-1){
        vi LIS;
        LIS.pb(subsequence[i]);
        maxSize = max(maxSize, check(LIS, subsequence, i, n, 1));
    }
    cout << maxSize;
}