#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cassert>
#include <cstddef>

#define REP(i,n) for(int (i)=0;(i)<(n);(i)++)
#define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
#define RREP(i,a) for(int (i)=(a)-1;(i)>=0;(i)--)
#define FORR(i,a,b) for(int (i)=(a)-1;(i)>=(b);(i)--)

typedef long long LL;
typedef unsigned long long ULL;

using namespace std;

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

int kh[8] = {1,2,-1,-2,1,2,-1,-2};
int kw[8] = {2,1,-2,-1,-2,-1,2,1};
int bh[4] = {1, -1, -1, 1};
int bw[4] = {1, 1, -1, -1};

int main(){
    int N; cin>>N;
    vector<int> a(N);
    REP(i,N) cin>>a[i];
    int cnt=0;
    RREP(i,N){
        if(a[i]==N-cnt) cnt++;
    }
    cout<<N-cnt<<endl;
}