#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    int arr[n*2];
    for (int i = 0;i < n*2;i++) {
        cin >> arr[i];
    }
    int max_value = 0;
    for (int i = 0;i < n*2;i++) {
        for (int j = i;j < n*2;j++) {
            if (arr[i] == arr[j] && i != j) {
                if (max_value < j-i-1) {
                    max_value = j-i-1;
                }
            }
        }
    }
    cout << max_value;
    return 0;
}