#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 200000
int max(int a, int b) { return a > b ? a : b; }
int *ej[N], *ec[N], eo[N];
void append(int i, int j, int c) {
int o = eo[i]++;
if (o >= 2 && (o & o - 1) == 0) {
ej[i] = (int *) realloc(ej[i], o * 2 * sizeof *ej[i]);
ec[i] = (int *) realloc(ec[i], o * 2 * sizeof *ec[i]);
}
ej[i][o] = j, ec[i][o] = c;
}
int dp[N][4];
void dfs(int p, int c_, int i) {
static int dp_[3][3];
int o, k, t;
for (o = eo[i]; o--; ) {
int j = ej[i][o], c = ec[i][o];
if (j != p)
dfs(i, c, j);
}
memset(dp_, -1, sizeof dp_), dp_[0][0] = 0;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p)
for (k = 2; k >= 0; k--)
for (t = 2; t >= 0; t--) {
int x = dp_[k][t];
if (x == -1)
continue;
if (dp[j][0] != -1)
dp_[k][t] = x + dp[j][0];
if (k < 2 && dp[j][1] != -1)
dp_[k + 1][t] = max(dp_[k + 1][t], x + dp[j][1]);
if (t == 0) {
if (dp[j][2] != -1)
dp_[k][1] = max(dp_[k][1], x + dp[j][2]);
if (k < 2 && dp[j][3] != -1)
dp_[k + 1][2] = max(dp_[k + 1][2], x + dp[j][3]);
}
}
}
dp[i][0] = dp_[1][0];
if (dp[i][0] != -1)
dp[i][0] += c_;
dp[i][0] = max(dp[i][0], dp_[0][0]);
dp[i][1] = dp_[0][0];
if (dp[i][1] != -1)
dp[i][1] += c_;
dp[i][2] = dp_[1][2];
if (dp[i][2] != -1)
dp[i][2] += c_;
dp[i][2] = max(dp[i][2], max(dp_[0][1], max(dp_[2][0], dp_[2][2])));
dp[i][3] = max(dp_[0][1], max(dp_[2][0], dp_[2][2]));
if (dp[i][3] != -1)
dp[i][3] += c_;
}
int main() {
int n, h, i, j, c;
scanf("%d", &n);
for (i = 0; i < n; i++) {
ej[i] = (int *) malloc(2 * sizeof *ej[i]);
ec[i] = (int *) malloc(2 * sizeof *ec[i]);
}
for (h = 0; h < n - 1; h++) {
scanf("%d%d%d", &i, &j, &c), i--, j--;
append(i, j, c), append(j, i, c);
}
dfs(-1, 0, 0);
printf("%d\n", max(dp[0][1], dp[0][3]));
return 0;
}
