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

typedef struct treenode
{
    int data;
    struct treenode *left;
    struct treenode *right;
}Node;
int count =0;
Node *root = NULL;
Node* create(int num)
{
    Node* newnode = (Node*)malloc(sizeof(Node));
    newnode->data = num;
    newnode->left = 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
    root->right = insert(root->right,num);
    return root;
}
int search(Node* root,int tar)
{
    if(root==NULL)
    return 0;
    
    if(root->data == tar)
    return 1;
    if(tar < root->data)
     return search(root->left,tar);
     else
      return search(root->right,tar);
}
int main()
{
    int n,num,tar;
    scanf("%d",&n);
    Node *root = NULL;
    if(n<=0)
    {
        printf("Invalid input");
        return 0;
    }
    for(int i=0;i<n;i++)
    {
        scanf("%d",&num)
        if(num < 0)
        {
            printf("Invalid input");
            return 0;
        }
        if(search(root,num)) continue;
        root = insert(root,num);
    }
    
    printf("%d",count);
    
    return 0;
}