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using System;
using System.Linq;
using System.Collections.Generic;

public class Solution {
    public int solution(int[] A, int[] B)
{
    int answer = 0;
    SortedDictionary<int, int> dictA = new SortedDictionary<int, int>();
    SortedSet<int> keys = new SortedSet<int>();

    for (int i = 0; i < B.Length; i++)
    {
        if (dictA.ContainsKey(B[i]))
            dictA[B[i]]++;
        else
            dictA.Add(B[i], 1);

        keys.Add(B[i]);
    }

    for (int i = 0; i < A.Length; i++)
    {
        if (dictA.Count == 0) break;

        int key;

        // A[i]보다 큰 값 찾기
        var view = keys.GetViewBetween(A[i] + 1, int.MaxValue);
        if (view.Count > 0)
        {
            key = view.Min;
            answer++;
        }
        else
            key = keys.Min; // A[i]보다 큰 값이 없으면 가장 작은 값 대입

        if (dictA[key] == 1)
        {
            dictA.Remove(key);
            keys.Remove(key);
        }
        else
            dictA[key]--;
    }
    return answer;
}
}