#include <stdio.h>
#include <stdlib.h>

#define ARRAY_NUM 100000

int main(void) {
	int i, n, max = 0, max1=0, max_num = 0, count = 0;
	int list[ARRAY_NUM] = { };

	scanf("%d", &n);
	for (i = 0; i < n; i++) {
		scanf("%d", &list[i]);
	}

	for (i = 0; i < n; i++) {
		if (max < list[i]) {
			max = list[i];
			max_num = i;
		}
	}

	max1 = max;

	for (count = 0; list[--max_num] == --max; count++) {
	}

	printf("%d", max1 - count);


	return 0;
}