#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001
int ans = 0;
vector<int> pos;

void go(int cur,int to){
	if(pos[cur]==to)return;
	go(cur-1,to);
	if(pos[cur-1]==to){
		swap(pos[cur-1],pos[cur]);
		ans++;
		return;
	}
	
	
}

int main(){
	
	int N;
	cin>>N;
	
	vector<int> P(N);
	pos.resize(N);
	rep(i,N){
		cin>>P[i];
		P[i]--;
		pos[P[i]] = i;
	}
	
	for(int i=N-1;i>=0;i--){
		go(i,i);
	}
	
	cout<<ans<<endl;
	
	return 0;
}