#include <stdio.h>

int main(void) {
	int N,A[1000],X;
	scanf("%d",&N);
	for(int i=1;i<N;i++){
		scanf("%d",&A[i]);
	}
	scanf("%d",&X);
	if(X-1==0){
		printf("-1");
	}else{
		printf("%d",A[X-1]);
	}
	return 0;
}