#include <stdio.h>
#include <vector>

using namespace std;

int main(void) {

	int N;
	while (scanf("%d", &N) == 1) {
				
		vector<int> vct(N);
		vector<int> pos(N+1);
		
		for (int i = 0; i < N; i++) {
		int tmp;
		
		scanf("%d", &tmp);
		pos[tmp] = i;
		vct[i] = tmp;
		}
		int c = 0;

		for (int i =0 ; i< N; i++) {
			if(vct[i] != i + 1) {
				int tmp;
				int idx = pos[i + 1];
				
				tmp = vct[i];
				vct[i] = vct[idx];
				vct[idx] = tmp;
				pos[i+1] = i;
				pos[tmp] = idx;
				
				
				++c;
			}
		
		}

		printf("%d\n", c);
		
	}

	return 0;
}