#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#define p(s) cout<<(s)<<endl
#define REP(i,n,N) for(int i=n;i<N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=n;i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define F first
#define S second
typedef long long ll;
using namespace std;
const int inf = 1e9+7;

int N;
int A[100010];
int main() {
    cin>>N;
    REP(i,0,N){
        cin>>A[i];
    }
    int now=N;
    RREP(i,0,N){
        if(A[i]==now){
            now--;
        }
    }
    p(now);
    return 0;

}