#include<stdio.h>
int main(){
	int m,n,i;
	scanf("%d",&m);
	int a[m];
	for(i=0;i<m;i++){
		scanf("%d",&a[i]);
	} 
	scanf("%d",&n);
	int f=0;
	for(i=0;i<m;i++){
		if(a[i]==n){
			f=1;
			break;
		}
	}
	if(f==0){
		printf("%d",-1);
	}else{
	    printf("%d",i+1);	
	}

	return 0;
	
}
/**************************************************************
	Problem: 1154
	User: admin
	Language: C
	Result: Accepted
	Time:18 ms
	Memory:1144 kb
****************************************************************/