#include<queue>

#include<cstdio>

#include<string>

#include<cstring>

#include<vector>

#include<iostream>

#include<algorithm>

#include<functional>

using namespace std;

const int maxn = 5e3 + ;

const int INF = 0x3f3f3f3f;

struct Edge{

    int value, flow, to, rev;

    Edge(){}

    Edge(int a, int b, int c, int d) :to(a), value(b), flow(c), rev(d){}

};

vector<Edge> vec[maxn];

inline void Add(int from, int to, int flow, int value){

    vec[from].push_back(Edge(to, value, flow, vec[to].size()));

    vec[to].push_back(Edge(from, -value, , vec[from].size() - ));

}

bool book[maxn];//用于SPFA中标记是否在queue中

int cost[maxn];//用于存费用的最短路径

int pre[maxn];//用于存前结点

int pree[maxn];//用于存钱结点的vector中的下标

bool Spfa(int from, int to){

    memset(book, false, sizeof book);

    memset(cost, INF, sizeof cost);

    book[from] = true;

    //cout << cost[0] << " " << INF << endl;

    cost[from] = ;

    queue<int>que;

    que.push(from);

    while (!que.empty()){

        int t = que.front();

        book[t] = false;

        que.pop();

        for (int i = ; i < vec[t].size(); i++){

            Edge& e = vec[t][i];

            if (e.flow> && cost[e.to] > cost[t] + e.value){

                cost[e.to] = cost[t] + e.value;

                pre[e.to] = t;

                pree[e.to] = i;

                if (book[e.to] == false){

                    que.push(e.to);

                    book[e.to] = true;

                }

            }

        }

    }

    return cost[to] != INF;

}

int Work(int from, int to){

    int sum = ;

    while (Spfa(from, to)){

        int mflow = INF;//SPFA找到最短路径的最小容量

        int flag = to;

        while (flag != from){

            mflow = min(mflow, vec[pre[flag]][pree[flag]].flow);

            flag = pre[flag];

        }

        flag = to;

        while (flag != from){

            //cout << flag << " " << pre[flag] << " " << mflow << " " << vec[pre[flag]][pree[flag]].value << endl;

            sum += vec[pre[flag]][pree[flag]].value*mflow;

            vec[pre[flag]][pree[flag]].flow -= mflow;

            vec[flag][vec[pre[flag]][pree[flag]].rev].flow += mflow;

            flag = pre[flag];

        }

    }

    return sum;

}

int main()

{

    ios::sync_with_stdio(false);

    int n, m, a, b;

    cin >> n >> m;

    for (int i = ; i <= n; i++){

        cin >> a >> b;

        Add(i, a + n, , );

        Add(i, b + n, , );

        Add(, i, , );

    }

    for (int i = ; i <= m; i++){

        for (int j = ; j <= ; j += ){

            Add(i + n, m + n + , , j);

        }

    }

    cout << Work(, m + n + ) << endl;

    return ;

}