#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(int i = (n) - 1; (i) >= 0; --i)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD LL(1e9 + 7)
#define INF 1000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;

int main() {
	int n;
	cin >> n;
	VI a(n);
	REP(i, n) 
		cin >> a[i];
	reverse(ALL(a));
	int ans = n;
	REP(i, n) {
		if (ans == a[i])
			ans--;
	}
	cout << ans << endl;
	return 0;
}