#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <set>
#include <utility>

using namespace std;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;

int main(){
    int N;
    string S;
    cin >> N >> S;

    vector<int> sumQ = {0};

    int v = 0, rev = 1, pos = 0;
    int hi = 0;
    int ans = 0;
    for(char c : S){
        int dx = 0;
        sumQ.push_back(sumQ.back());
        if(c == '-') dx = -1;
        if(c == '+') dx = 1;
        dx *= rev;
        if(c == '?'){ dx = 1; hi++; }
        v += dx;
        hi = max(hi, v);
        if(v < 0){
            ans++;
            v = hi*2 + 1;
            rev *= -1;
            hi = v;
        }
        pos++;
    }

    ans = (ans + 1) / 2;
    cout << ans << '\n';
    return 0;
}


struct ios_do_not_sync{
    ios_do_not_sync(){
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
    }
} ios_do_not_sync_instance;