#include<stdio.h>
int main(){
	freopen ("carti1.in", "r", stdin);
	freopen ("carti1.out", "w", stdout);

	int n, i, v[200001], z=1, p=0;

	scanf("%d ", &n);

	for(i=1; i<=n; i++){
		scanf("%d ", &v[i]);
	}

	while(z<=n){
		for(i=1; i<=n; i++){
			if(v[i]==z){
				z++;
				if(z==n){
					//continue;
					printf("%d ", p);
					return 0;
				}
			}
		}
		p++;
	}

	printf("%d ", --p);
	return 0;
}