#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll,ll> pl;
typedef vector<pl> vp;
#define fore(i,a,b) for(ll i=(ll)(a);i<=(ll)(b);++i)
#define rep(i,n) fore(i,0,(n)-1)
#define rfore(i,a,b) for(ll i=(ll)(b);i>=(ll)(a);--i)
#define rrep(i,n) rfore(i,0,(n)-1)
#define all(x) (x).begin(),(x).end()
const ll INF=1001001001;
const ll LINF=1001001001001001001;
const ll D4[]={0,1,0,-1,0};
const ll D8[]={0,1,1,0,-1,-1,1,-1,0};
template<class T>
bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T>
bool chmin(T &a,const T &b){if(b<a){a=b;return 1;}return 0;}

void solve(){
    ll n;cin>>n;
    vl a(n);rep(i,n)cin>>a[i];

    ll idx=n;
    rrep(i,n)if(a[i]==idx)idx--;
    cout<<idx<<endl;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    solve();
}