import java.math.*;
import java.util.*;
import java.io.*;

class Main
{
    public static void main(String[] args)
    {
        new Main().run();
    }
    
    void run() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long[] B = new long[N];
        for (int i = 0; i < N; ++i) {
            B[i] = sc.nextLong();
        }
        long ans = 0;
        long a = 0;
        for (int i = 0; i < N; ++i) {
            ans += Math.abs(a);
            a += B[i] - 1;
        }
        System.out.println(ans);
            
    }
    
    void tr(Object...o){
        System.out.println(Arrays.deepToString(o));
    }

    
}