#include<bits/stdc++.h>
using namespace std;

#define all(v) v.begin(),v.end()
using ll = long long;
const ll INF=1ll<<60;
using vll = vector<ll>;

int main(){
    ll N;
    cin>>N;
    vll A(N),ind(N);
    for(int i=0;i<N;i++){
        cin>>A[i];
        A[i]--;
        ind[A[i]]=i;
    }
    ll now=ind[N-1];
    ll ans=N-1;
    while(ans>0){
        if(now<ind[ans-1])break;
        ans--;
        now=ind[ans];
    } 
    cout << ans << endl;
}