1 #include <bits/stdc++.h>
2 using namespace std;
3 const int inf=0x3f3f3f3f;
4 typedef long long ll;
5 const int M=300001;
6 const int N=100001;
7 struct node {
8 int u, v, w, k;
9 bool operator<(const node &b) const {
10 return w < b.w;
11 }
12 }a[M];
13 struct node1 {
14 int to,next,w;
15 }e[M];
16 int n,m,mn=inf,t,head[N],f[N][20],d1[N][20],d2[N][20],deep[N];
17
18 void add(int u,int v,int w){
19 t++;
20 e[t].to=v;
21 e[t].w=w;
22 e[t].next=head[u];
23 head[u]=t;
24 }
25
26 struct Kurskal {
27 int n, m,f[N];
28 int find(int x) {
29 return x == f[x] ? x : f[x] = find(f[x]);
30 }
31
32 ll kurskal() {
33 int k = 0;
34 ll ans=0;
35 sort(a + 1, a + m + 1);
36 for (int i = 1; i <= m; i++) {
37 int x = find(a[i].u), y = find(a[i].v);
38 if (x != y) {
39 ans += a[i].w;
40 a[i].k=1;
41 add(a[i].u, a[i].v, a[i].w);
42 add(a[i].v, a[i].u, a[i].w);
43 f[x] = y;
44 k++;
45 if (k == n - 1) {
46 break;
47 }
48 }
49 }
50 return ans;
51 }
52
53 void init(int n, int m) {
54 this->n = n;
55 this->m = m;
56 for (int i = 1; i <= n; i++) {
57 f[i] = i;
58 }
59 for (int i = 1; i <= m; i++) {
60 scanf("%d%d%d", &a[i].u, &a[i].v, &a[i].w);
61 }
62 }
63 } K;
64
65
66 void dfs(int x,int fa) {
67 for (int i = 1; i <= 16; i++) {
68 if (deep[x] < (1 << i)) break;
69 f[x][i] = f[f[x][i - 1]][i - 1];
70 d1[x][i] = max(d1[x][i - 1], d1[f[x][i - 1]][i - 1]);
71 if (d1[x][i - 1] == d1[f[x][i - 1]][i - 1]) {
72 d2[x][i] = max(d2[x][i - 1], d2[f[x][i - 1]][i - 1]);
73 } else {
74 d2[x][i] = min(d1[x][i - 1], d1[f[x][i - 1]][i - 1]);
75 d2[x][i] = max(d2[x][i - 1], d2[x][i]);
76 d2[x][i] = max(d2[x][i], d2[f[x][i - 1]][i - 1]);
77 }
78 }
79 for (int i = head[x]; i; i = e[i].next) {
80 int to = e[i].to;
81 if (to != fa) {
82 f[to][0] = x;
83 d1[to][0] = e[i].w;
84 deep[to] = deep[x] + 1;
85 dfs(to, x);
86 }
87 }
88 }
89
90
91 int lca(int x,int y) {
92 if (deep[x] < deep[y]) {
93 swap(x, y);
94 }
95 int h = deep[x] - deep[y], k = 0;
96 while (h) {
97 if (h & 1) {
98 x = f[x][k];
99 }
100 h >>= 1;
101 k++;
102 }
103 if (x == y) {
104 return x;
105 }
106 for (int k = 19; k >= 0; k--) {
107 if (f[x][k] != f[y][k]) {
108 x = f[x][k];
109 y = f[y][k];
110 }
111 }
112 return f[x][0];
113 }
114
115
116 void cal(int x,int fa,int v) {
117 int mx1 = 0,mx2 = 0;
118 int h = deep[x] - deep[fa];
119 for (int i = 0; i <= 16; i++) {
120 if (h & (1 << i)) {
121 if (d1[x][i] > mx1) {
122 mx2 = mx1;
123 mx1 = d1[x][i];
124 }
125 mx2 = max(mx2, d2[x][i]);
126 x = f[x][i];
127 }
128 }
129 if (mx1 != v) {
130 mn = min(mn, v - mx1);
131 } else {
132 mn = min(mn, v - mx2);
133 }
134 }
135
136 void solve(int i,int v){
137 int x=a[i].u,y=a[i].v,f=lca(x,y);
138 cal(x,f,v);
139 cal(y,f,v);
140 }
141
142 int main() {
143 scanf("%d%d", &n, &m);
144 K.init(n,m);
145 ll ans = K.kurskal();
146 dfs(1, 0);
147 for (int i = 1; i <= m; i++) {
148 if (!a[i].k) {
149 solve(i, a[i].w);
150 }
151 }
152 printf("%lld
", ans + mn);
153 return 0;
154 }
