#include <stdio.h>
#define MAX 100002

void insertion_sort(int tiparr[], int tip, int count);

int main(void) {

    int N = 0;
   
    scanf("%d", &N);
    long long sum = 0;
    int tiparr[MAX] = { 0 };
    int count = 0;
    
    for (int i = 0; i < N; i++)
    {
        int tip = 0;
        scanf("%d", &tip);

        
        insertion_sort(tiparr, tip, count);

        count++;
    }
    for (int i = 0; i < N ; i++)
    {
        if (tiparr[i] - i <= 0)
        {
            break;
        }
        else if(tiparr[i] -i > 0)
        {
            sum += tiparr[i] - i;
        }
    }

    printf("%lld", sum);

    return 0;
}

void insertion_sort(int tiparr[], int tip, int count)
{
    tiparr[count] = tip;
    int j = count;
    
    while (j>0&&tiparr[j-1] < tiparr[j])
    {
        int temp = tiparr[j - 1];
        tiparr[j - 1] = tiparr[j];
        tiparr[j] = temp;
        j--;
    }
    
 
}```