3. Поворот на МЕГУ

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int k = sc.nextInt();
        int n = sc.nextInt();
        int sum = 0;
        int cars = 0;
        for (int i = 0; i < n; i++) {
            cars = sc.nextInt();

            sum += cars;
            sum -= k;
            if (sum < 0) sum = 0;
        }
        System.out.println(sum);
    }
}