《CF767C Garland》

难顶，这题其实不难，但是细节问题出的有点多。

考虑删的两条边的相对位置，如果他们的LCA不等于他们，那么很显然就是LCA的两个子树里删边。

如果LCA = 其中一条边，那么就有LCA = 2 * average,然后子树内再删一条。这里记录一下子树里 = average / 3的即可。

emmm细节有点多。

// Author: levil
#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
typedef long double ld;
typedef pair<int,int> pii;
const int N = 1e6 + 5;
const int M = 1e4 + 5;
const LL Mod = 998244353;
#define rep(at,am,as) for(int at = am;at <= as;++at)
#define ret(at,am,as) for(int at = am;at >= as;--at)
#define INF 1e9
#define dbg(ax) cout << "now this num is " << ax << endl;
inline long long ADD(long long x,long long y) {
    if(x + y < 0) return ((x + y) % Mod + Mod) % Mod;
    return (x + y) % Mod;
}
inline long long MUL(long long x,long long y) {
    if(x * y < 0) return ((x * y) % Mod + Mod) % Mod;
    return x * y % Mod;
}
inline long long DEC(long long x,long long y) {
    if(x - y < 0) return (x - y + Mod) % Mod;
    return (x - y) % Mod;
}

int n,rt,val[N],now,dp[N],vis[N];
vector<pii> G[N];
void dfs(int u,int fa,int id) {
    dp[u] = val[u];
    vector<int> vec;
    for(auto v : G[u]) {
        if(v.first == fa) continue;
        dfs(v.first,u,v.second);
        if(vis[v.first]) vec.push_back(vis[v.first]);
        dp[u] += dp[v.first];
    }
    if(vec.size() > 1) {
        printf("%d %d\n",vec[0],vec[1]);
        exit(0);
    }
    else if(u != rt && dp[u] == 2 * now && vec.size() > 0) {
        printf("%d %d\n",id,vec[0]);
        exit(0);
    }
    if(dp[u] == now) vis[u] = id;
    else if(vec.size() > 0) vis[u] = vec[0];
}
void solve() {
    scanf("%d",&n);
    int sum = 0;
    rep(i,1,n) {
        int x,y;scanf("%d %d",&x,&y);
        val[i] = y;
        if(x == 0) rt = i;
        else {
            G[x].push_back(pii{i,i});
            G[i].push_back(pii{x,i});
        }
        sum += val[i];
    }
    if(sum % 3 != 0) {printf("-1\n");exit(0);}
    now = sum / 3;
    dfs(rt,0,0);
    printf("-1\n");
}   
int main() {
    //int _;
    //for(scanf("%d",&_);_;_--) {
        solve();
    //}
    system("pause");
    return 0;
}
/*
3
0 1
1 2
1 3


*/