#include<stdio.h>
#include<stdlib.h>
typedef struct node
{
    int data;
    struct  node *left,*right;
}Node;
Node *root=NULL;
Node *create(int num)
{
    Node *newNode=(Node*)malloc(sizeof(Node));
    newNode->data=num;
    newNode->left=NULL;
    newNode->right=NULL;
    return newNode;
}
Node *insert(Node *root,int num)
{
    if(root==NULL)
        return create(num);
    if(num<root->data)
        root->left=insert(root->left,num);
    else if(num>root->data)
        root->right=insert(root->right,num);
        return root;
}
Node *postorder(Node *root)
{
    if(root->left==NULL && root->right==NULL)
    {
        postorder(root->left);
    }
}
int main()
{
    int size,num,itr;
    scanf("%d",&size);
    if(size<=0)
    {
        printf("Invalid input");
        return 0;
    }
    for(itr=0;itr<=size;itr++)
    {
        scanf("%d",&num);
        root=insert(root,num);
    }
    printf("%d",postorder(root)->left);
    return 0;
}