#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include<vector>
#include <algorithm>
using namespace std;
const int N = 1e3+20, M = 1e2+10, mod = 1e9+7, inf = 1e9+1000;
typedef long long ll;

struct edge{int to,next,w;}e[N * 4];
int head[N] , t , n , m , cost, dp[N];
void add(int u,int v,int w) {e[t].to=v,e[t].w=w,e[t].next=head[u];head[u]=t++;}
void init() {t=1;memset(head,-1,sizeof(head));}
void dfs(int u,int fa,int limit) {
    int ret = 0, cnt = 0;
    for(int i=head[u];i!=-1;i=e[i].next) {
        int to = e[i].to;
        int value = e[i].w;
        if(to == fa) continue;
        cnt += 1;
        dfs(to,u,limit);
        if(dp[to] == -1) {
            if(value <= limit) ret += value;
            else return ;
        }else {
            if(value <= limit) ret += min(dp[to] , value);
            else ret += dp[to];
        }
    }
    if(cnt)dp[u] = ret;
}
int check(int limit) {
    memset(dp,-1,sizeof(dp));
    dfs(1,-1,limit);
    if(dp[1] == -1) return 0;
    else {
        cost = dp[1];
        return 1;
    }
}
int main()
{
    while(~scanf("%d%d",&n,&m)) {
        if(!n&&!m) break;
        int mx = 0;
        init();
        for(int i=1;i<n;i++) {
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            mx = max(c,mx);
            add(a,b,c);
            add(b,a,c);
        }
        int l = 0, r = mx, ans = -1;
        while(l<=r) {
            int mid = (l+r) / 2;
            cost = 0;
            int OK = check(mid);
            if(OK && cost <= m) {
                r = mid - 1;
                ans = mid;
            }else {
                l = mid + 1;
            }
        }
        if(ans == -1) puts("-1");
        else if(check(ans)&&cost <= m) cout<<ans<<endl;
        else puts("-1");
    }
}