#include <stdio.h>
#include <stdbool.h>
#define rep(i, n) for (i = 0; i < n; i++)

int main() {
	int n;
	scanf("%d", &n);

	int i, a, ia, cnt = 1, t = -1;
	rep(i, n) {
		scanf("%d", &a);
		if (i == 0) ia = a;
		if (a == t + 1) { cnt++; t++; }
		else if (a > t + 1) { t = a; cnt = 1; }
	}

	int ans = n - cnt;
	if (ia == n - cnt) ans--;

	printf("%d\n", ans);
	return 0;
}