#include <stdio.h>
int main(void){
	int count=0,i,j=1,a[100000]={},n;
	scanf("%d",&n);
	for(i=0;i<n;i++){
		scanf("%d",&a[i]);
	}
	i=0;
	while(j<n){
		if(a[i]!=j){
			count++;
			i--;
		}
		i++;
		j++;
	}
	printf("%d",count);
}