#include <bits/stdc++.h>
int pickCoupons(int n, vector<int> &coupons)            //  2 Pointers Solution
{
    int l = 0;
    unordered_map<int, int> mp;
    int ans = INT_MAX;
    for (int r = 0; r < n; r++) { // using map for sliding window
        mp[coupons[r]]++;
        while (mp[coupons[r]] > 1) {
    /*
            once the occurrence of coupons[r] > 1 this means there are more than 1 of the same coupon
            then we will check the answer
            and remove the left side till the occurrence return to 1 : mp[coupons[r]] == 1
    */
            ans = min(ans, r - l + 1);
            mp[coupons[l]]--;
            l++;
        }
    }
    return (ans == INT_MAX ? -1 : ans);
}