#include<stdio.h>
#include<stdlib.h>

typedef struct TreeNode{
    int data;
    struct TreeNode *left;
    struct TreeNode *right;
}Node;

Node* create(int num){
    Node* newnode = (Node*)malloc(sizeof(Node));
    newnode->data = num;
    newnode->left = newnode->right = NULL;
    return newnode;
}
Node* insertBST(Node* root,int num){
    if(root==NULL){
        return create(num);
    }
    if(num < root->data){
        root->left = insertBST(root->left,num);
    }
    else{
        root->right = insertBST(root->right,num);
    }
    return root;
}

void min(Node* root,int num){
    if(root==NULL){
        return ;
    }
    while(root!=NULL){
            if(root->left==NULL){
              printf("%d",root->data);
              break;
            }  
    }
    return;
}
int main(){
    int size;
    Node* root=NULL;
    scanf("%d",&size);
    int num;
    for(int i=0; i<size; i++){
        scanf("%d",&num);
        if(!num){
            printf("Invalid input");
            return 0;
        }
            root = insertBST(root,num);
    }
    min(root,num);
    return 0;
}