//看看会不会爆int!数组会不会少了一维！

//取物问题一定要小心先手胜利的条件

#include <bits/stdc++.h>

using namespace std;

#define LL long long

#define ALL(a) a.begin(), a.end()

#define pb push_back

#define mk make_pair

#define fi first

#define se second

const int maxn =  + ;

const int inf = 0x3f3f3f3f;

struct Edge{

    int u, v, val1, val2;

    Edge(int u = , int v = , int v1 = , int v2 = ): u(u), v(v), val1(v1), val2(v2){}

    bool operator < (const Edge &a) const{

        if (val1 != a.val1) return val1 < a.val1;

        return val2 < a.val2;

    }

}e[maxn * ];

int n, k, m;

int par[maxn];

int pfind(int x){

    if (par[x] == x) return x;

    return par[x] = pfind(par[x]);

}

bool judge(int midval){

    for (int i = ; i <= n; i++) par[i] = i;

    int cnt1 = , cnt = ;

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

        Edge a = e[i];

        int pu = pfind(a.u), pv = pfind(a.v);

        if (pu == pv) continue;

        if (a.val1 <= midval) cnt1++, cnt++, par[pu] = pv;

        else if (a.val2 <= midval) cnt++, par[pu] = pv;

    }

    if (cnt == n- && cnt1 >= k) return true;

    return false;

}

int main(){

    scanf("%d%d%d", &n, &k, &m);

    int lb = , rb = ;

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

        int u, v, v1, v2;

        scanf("%d%d%d%d", &u, &v, &v1, &v2);

        e[i] = Edge(u, v, v1, v2);

    }

    sort(e + , e + m);

    while (lb < rb){

        int mid = lb + (rb - lb) / ;

        if (judge(mid)){

            rb = mid;

        }

        else {

            lb = mid + ;

        }

    }

    printf("%d\n", lb);

    return ;

}

/*

3 1 3

1 2 11 4

2 3 10 2

*/