source_code: import java.util.Scanner;
  
  public class Main{
  	public static void main(String[] args) {
  		Scanner sc=new Scanner(System.in);
  		while(sc.hasNext()) {
  			int n=sc.nextInt();
  			String s=sc.next();
  			int sum=0;
  			for(int i=0;i<s.length();i++) {
  				if(s.charAt(i)=='+') {
  					sum++;
  				}
  				if(s.charAt(i)=='-'&&sum!=0) {
  					sum--;
  				}
  			}
  			System.out.println(sum);
  		}
  	}
  }