Codeforces Round #398 (Div. 2) C. Garland

#include<bits/stdc++.h>

using namespace std;

#define X first
#define Y second
#define eps  1e-2
#define gcd __gcd
#define pb push_back
#define PI acos(-1.0)
#define lowbit(x) (x)&(-x)
#define bug printf("!!!!!\n");
#define mem(x,y) memset(x,y,sizeof(x))

typedef long long LL;
typedef long double LD;
typedef pair<int,int> pii;
typedef unsigned long long uLL;

const int maxn = 1e6+2;
const int INF  = 1<<30;
const int mod  = 1e9+7;

int a[maxn],n;
std::vector<int> g[maxn];
int rt=0,sum=0;
vector<int> res;

void dfs(int x,int fa){
    for(int i=0;i<g[x].size();i++){
        int to=g[x][i];
        if(to==fa) continue; 
        dfs(to,x);
        a[x]+=a[to];
    }
    if(a[x]==sum/3){
        a[x]=0;
        res.push_back(x);
    }
}

void solve(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        int v,val;scanf("%d%d",&v,&val);
        if(v==0) rt=i;
        else{
            g[v].push_back(i);
            g[i].push_back(v);
        }
        a[i]=val;
        sum+=val;
    }
    if(sum%3){cout<<-1<<endl;return;}
    dfs(rt,-1);
    if(res.size()>=3){
        cout<<res[0]<<" "<<res[1]<<endl;
    }else{
        cout<<-1<<endl;
    }
    return;
}

int main()
{
//    freopen("in.txt","r",stdin);
//    freopen("out.txt","w",stdout);
//    ios::sync_with_stdio(false);
    int t = 1;
    //scanf("%d",&t);
    while(t--){
    //    printf("Case %d: ",cas++);
        solve();
    }
    return 0;
}