import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Solution to Overdraft
 * 
 * @author vanb
 */
public class overdraft_vanb
{
    /** Input. */
    private static Scanner sc;
    
    /** Output. */
    private static PrintStream ps;
    
    /**
     * Do it!
     */
    private void doit()
    {
        int n = sc.nextInt();
        
        // We've got to make sure we can cover the worst balance.
        int balance = 0;
        int worst = 0;        
        while( n-->0 )
        {
            int t = sc.nextInt();
            balance += t;
            worst = Math.min( worst, balance );
        }
        
        // If the worst is -5, then we need to start with a balance of 5.
        // But, if the worst is 3, we don't start with a balance of -3, we start with 0.
        // A negative balance makes no sense.
        ps.println( Math.max( 0, -worst ) );
    }
        
    /**
     * Main.
     * 
     * @param args unused
     * @throws Exception
     */
    public static void main( String[] args ) throws Exception
    {
        sc = new Scanner( System.in );
        ps = System.out;
        
        new overdraft_vanb().doit();
    }

}