#include<stdio.h>
#include<stdlib.h>
typedef struct node
{
    int data;
    struct node*next;
}node;
node *head=NULL,*tail;
void create(int num)
{
    node*newnode=(node*)malloc(1*sizeof(node));
    newnode->data=num;
    newnode->next=NULL;
    if(head==NULL)
    {
        head=newnode;
        tail=newnode;
    }
    else
    {
        tail->next=newnode;
        tail=newnode;
    }
}
void display(int val)
{
    node*ptr=head;
    int pos=1;
    int found=0;
    while(ptr!=NULL)
    {
        if(ptr->data==val)
        {
            printf("%d",pos);
            found=1;
            break;

        }
        ptr=ptr->next;
        pos++;
    }
    if(!found)
    {
        printf("-1\n");
    }
}
int main()
{
    int s,n,i,val;
    scanf("%d",&s);
    for(i=0;i<s;i++)
    {
        scanf("%c",&n);
        create(n);
    }
    scanf("%d",&val);
    display(val);
    return 0;
}