#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcount
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC
const int N = 2e5 + 7;
vector <ii> g[N];
int sum[N];
void dfs1(int u, int p) {
for (auto e : g[u]) {
int v = e.f, c = e.s;
if (v != p) {
dfs1(v, u);
sum[u] += sum[v] + c;
}
}
}
const int INF = 1e18;
int ans = INF;
void dfs2(int u, int p, int up) {
for (auto e : g[u]) {
int v = e.f, c = e.s;
if (v == p) {
up += c;
}
}
ans = min(ans, up + sum[u]);
for (auto e : g[u]) {
int v = e.f, c = e.s;
if (v != p) {
dfs2(v, u, up + sum[u] - sum[v] - c);
}
}
}
signed main() {
#ifdef HOME
freopen("input.txt", "r", stdin);
#else
#define endl '\n'
ios_base::sync_with_stdio(0); cin.tie(0);
#endif
int n;
cin >> n;
for (int i = 0; i < n - 1; ++i) {
int u, v, a, b;
cin >> u >> v >> a >> b;
g[u].app(mp(v, a));
g[v].app(mp(u, b));
}
dfs1(1, 1);
dfs2(1, 1, 0);
cout << ans << endl;
}
