#include<bits/stdc++.h>
using namespace std;
using ll =long long;



int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll N;
    string S;
    cin>>N>>S;
    ll p=0,m=0,an=0;
    for(int i=0;i<N;i++)if(S[i]=='+')p++;
    for(int i=0;i<N;i++){
        
        if(S[i]=='-')m++;
        an=max(an,p+m+(S[i]=='0'));
        if(S[i]=='+')p--;
    }
    cout<<an<<"\n";
}