#include "bits/stdc++.h"
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
typedef long long ll;
typedef pair<int, int> PI;
typedef pair<int, PI> V;
typedef vector<int> VE;
const ll mod = 100000000000;

int main() {
  int n;
  cin >> n;
  int m=n;
  VE a(n);
  REP(i,n)cin>>a[i];
  REP(i,n){
    //print(a[n-i]);
    if(a[n-i]==m){
      //print("-")
      m--;
    }
  }
  print(m-1);
}