import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int [] A = new int [N];
        int sum =0;
        for(int i=0; i<N; i++){
            A[i] = sc.nextInt();
            sum+=A[i];
        }
        int p = (int)Math.sqrt(sum);
        int z = 2*p-1;
        int move = 0;
        for(int i=0; i<N; i++){
            if(i<=p-1){
                int t=A[i]-(i+1);
                if(t>0){
                    move+=t;
                }
            }else if(i<=z-1){
                int t=A[i]-(z-i);
                if(t>0){
                    move+=t;
                }
            }else{
                move+=A[i];
            }
        }
        System.out.println(move);
    }
}