#include <bits/stdc++.h>
#define REP(i,n) for(int i = 0; i < (int)(n); ++i)
using namespace std;
int a[100001], b[100001];

int main() {
    int N;
    cin >> N;
    REP(i,N){
        cin >> a[i];
        b[a[i]-1] = i;
    }
    
    int ans = 0;
    REP(i,N-1){
        if(b[i]>b[i+1]) ans = i+1;
    }
    
    cout << ans << endl;
    return 0;
}