#include <bits/stdc++.h>

using namespace std;

int main() {
	int n;
	long long max;
	ios::sync_with_stdio(false);
	vector<int> arr;
	while(scanf("%d", &n) == 1) {
		max = 0;
		arr.clear();
		arr.resize(n);
		for(int i = 0; i < n; i++) {
			scanf("%d",&arr[i]);
		}
		int p = 0;
		while(arr[p] != (p+1) && p < n) {
			swap(arr[p], arr[arr[p]-1]);
			max++;
			while(arr[p] == (p+1) && p < n) p++;
		}
		cout << max << endl;
	}
	return 0;
}