题解

#include<iostream>
#include<unordered_set>
using namespace std;
int main(){
    int n;
    cin>>n;
    unordered_set<int>s;
    for (int i=0;i<n;i++){
        int x;
        cin>>x;
        s.insert(x);
    }
    cout<<s.size();
    return 0;
}