#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <map>

using namespace std;

#define INF 		2000000007
#define MOD			1000003

#define MAX 		105

#define REP(i,n)	for(int i=0;i<(n);++i)
#define REPS(i,s,t)	for(int i=(s);i<(t);++i)

typedef unsigned int 			uint;
typedef unsigned long long int	ull;

vector<int> prime(int N){
	int cnt = 1;
	vector<int> pn(N+1);
	REPS(i,N,1) pn[i]=i;
	for(int i=4;i<N;i+=2) pn[i] = -1; 
	for(int i=3;i<N;i+=2){
		if (pn[i]==-1) continue;
		for(int j=i*2;j<=N;j+=i) pn[j]= -1;
		++cnt;
	}
	// 整頓
	vector<int> p(cnt);
	for(int i=0,j=2;j<N;++j){
		if(pn[j]!=-1)p[i++]=j;
	}
	return p;
}

int index(vector<int> &array,int num){
	for(int i=0;i<array.size();++i){
		if(array[i]==num)return i;
	}
	return -1;
}

int main(){
	int N;cin>>N;

	vector<int> a(N+2);
	REPS(i,1,N+1) cin>>a[i];

	int cnt=N;
	for(int i=N;i>0;--i){
		if(a[i]==cnt)--cnt;
	}
	cout << cnt << endl;
	return 0;
}