C - Good Sequence atcoder solution

 

problem: https://atcoder.jp/contests/abc082/tasks/arc087_a?lang=en

#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/tree_policy.hpp>

using namespace std;

using namespace __gnu_pbds;

template <class type1>

#define ll long long int

#define endl "\n"

#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>

using ordered_multiset = tree <type1, null_type, less_equal <type1>, rb_tree_tag, tree_order_statistics_node_update>;

 //ordered_multiset <ll> kek;(declaration for multiorder set)

// ordered_set o_set;(declaration)

//kek.order_of_key(i);(strictly less then i for multi order set)

//o_set.order_of_key(5) ;(strictly less then i for multi order set)

#define yes cout << "YES\n"

#define no cout << "NO\n"

int main()

{

    ios_base::sync_with_stdio(0);

    cin.tie(0);

    cout.tie(0);

   

     ll n;

     cin>>n;

     map<ll,ll>mp;

     ll ans=0;

     for(ll i=0;i<n;i++)

     {

          ll r;

          cin>>r;

          mp[r]++;

     }

     for(auto u:mp)

     {

        if(u.first!=u.second)

        {

            if(u.first>u.second)ans+=u.second;

            else ans+=(u.second-u.first);

        }

     }

     cout<<ans<<endl;

    return 0;

}