#include "dreaming.h"
#include <iostream>
#include <cstdio>
#include <vector>
#define SZ 100005
using namespace std;
int MM = 2e9;
int n, m, mx, po, cnt, mn, md, ans, m1, m2, m3, v[SZ], h1[SZ], h2[SZ], num1[SZ], num2[SZ];
vector<int> a[SZ], b[SZ], c;
//void f(int p, int q, int w) {
// int i, t;
// if (w > mx) {
// mx = w;
// po = p;
// }
// v[p] = cnt;
// for (i = 0; i < a[p].size(); i++) {
// t = a[p][i];
// if (t == q) continue;
// f(t, p, w + b[p][i]);
// }
//}
//
//int g(int p, int q, int w) {
// int i, t, t2;
// if (w == mx) return 1;
// for (i = 0; i < a[p].size(); i++) {
// t = a[p][i];
// if (t == q) continue;
// if (g(t, p, w + b[p][i])) {
// t2 = max(w, mx - w);
// mn = min(mn, t2);
// return 1;
// }
// }
// return 0;
//}
int f(int p, int q) {
int i, t, mx1 = 0, mx2 = 0, t2, n1, n2;
v[p] = cnt;
for (i =0 ; i < a[p].size(); i++) {
t = a[p][i];
if (t == q) continue;
t2 = f(t, p) + b[p][i];
if (t2 > mx1) {
n2 = n1;
n1 = t;
mx2 = mx1;
mx1 = t2;
} else if (t2 > mx2) {
mx2 = t2;
n2 = t;
}
}
h1[p] = mx1;
h2[p] = mx2;
num1[p] = n1;
num2[p] = n2;
return mx1;
}
int g(int p, int q, int w) {
int i, t, tt, t1, mx1 = 0;
for (i = 0; i < a[p].size(); i++) {
t = a[p][i];
if (t == q) continue;
if (num1[p] == t) t1 = h2[p];
else t1 = h1[p];
t1 = max(t1, w);
mx1 = max(mx1, g(t, p, t1 + b[p][i]) + b[p][i]);
}
tt = max(w, mx1);
mx = max(mx, tt);
mn = min(mn, tt);
return mx1;
}
int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
int i, j, t1, t2, t3;
n = N;
m = M;
for (i = 0; i < m; i++) {
// scanf ("%d %d %d", &t1, &t2, &t3);
t1 = A[i];
t2 = B[i];
t3 = T[i];
a[t1].push_back(t2);
a[t2].push_back(t1);
b[t1].push_back(t3);
b[t2].push_back(t3);
}
for (i = 0; i < n; i++) {
if (v[i]) continue;
cnt++;
mx = 0;
mn = MM;
f(i, 0);
g(i, 0, 0);
// mx = -1;
// c.clear();
// f(i, 0, 0);
// c.push_back(po);
// mx = -1;
// f(po, 0, 0);
// ans = max(ans, mx);
// c.push_back(po);
// if (mx == 0) {
// continue;
// }
// mn = MM;
// g(c[0], 0, 0);
if (mn > m1) {
m3 = m2;
m2 = m1;
m1 = mn;
} else if (mn > m2) {
m3 = m2;
m2 = mn;
} else if (mn > m3) {
m3 = mn;
}
ans = max(ans, mx);
// printf("%d %d\n", c[0], c[1]);
}
if (m == n - 1) {
cout << ans;
return 0;
}
ans = max(ans, m1 + m2 + L);
if (cnt >= 3) ans = max(ans, m2 + m3 + L * 2);
return ans;
}
