#include<queue>
#include<cstdio>
#include<string>
#include<cstring>
#include<vector>
#include<iostream>
#include<algorithm>
#include<functional>using namespace std;const int maxn = 5e3 + 5;
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, 0, vec[from].size() - 1));
}
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] = 0;queue<int>que;que.push(from);while (!que.empty()){int t = que.front();book[t] = false;que.pop();for (int i = 0; i < vec[t].size(); i++){Edge& e = vec[t][i];if (e.flow>0 && 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 = 0;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 = 1; i <= n; i++){cin >> a >> b;Add(i, a + n, 1, 0);Add(i, b + n, 1, 0);Add(0, i, 1, 0);}for (int i = 1; i <= m; i++){for (int j = 1; j <= 99; j += 2){Add(i + n, m + n + 1, 1, j);}}cout << Work(0, m + n + 1) << endl;return 0;
}