#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#define  _SCL_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
#include <cstdint>
#define REP(i,n) for(int i = 0;i < n;++i)
using namespace std;
int a[1000000] = {};
int main() {
	int n;
	scanf("%d", &n);
	REP(i, n) scanf("%d", &a[i]);
	int counter = 0;
	int now_max = n;
	for (int i = n - 1;i >= 0;--i) {
		if (now_max != a[i]) {
			counter++;
		}
		else {
			now_max--;
		}
	}
	cout << now_max << endl;
	return 0;
}