#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll mod = 1e9 + 7;
const int N = 200005;
const int INF = 0x3f3f3f3f;

int main() {
    int n;
    string s;
    cin >> n >> s;
    vector<int> vec;
    int p1 = -INF, p2 = 1;
    for (int i = 0; i < n; i++) {
        if (s[i] == '-') {
            vec.push_back(p1);
            p1++;
        } else if (s[i] == '+') {
            vec.push_back(p2);
            p2++;
        } else {
            vec.push_back(0);
        }
    }
    auto end = vec.begin();
    for (auto x : vec) {
        auto it = lower_bound(vec.begin(), end, x);
        *it = x;
        if (it == end) end++;
    }
    cout << end - vec.begin() << "\n";
    return 0;
}