Submission #19502252

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#include <math.h>
#include <iomanip>
#include <cstdint>
#include <string>
#include <sstream>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
#define rep(i,n) for (int i = 0; i < (n); ++i)
typedef long long ll;
using P = pair<ll,ll>;

const int INF=1001001001;
const int mod =1e9+7;

vector<vector<int>>G;
vector<int>C;
int dfs(int i){
  if(C[i]>0){return C[i];}
  int mn=INF;
  for(int nc:G[i]){
    chmin(mn,dfs(nc));
  }
  return C[i]=mn;
}
ll ans;
void dfs2(int i){
  for(int nc:G[i]){
    dfs2(nc);
    ans+=C[nc]-C[i];
  }
}
int main() {
  int N,M;
  cin>>N>>M;
  G.resize(N);
  for(int i=1;i<N;i++){
    int p;
    cin>>p;
    G[p].push_back(i);
  }
  C.resize(N);
  rep(i,M){
    int b,c;
    cin>>b>>c;
    C[b]=c;
  }
  dfs(0);
  C[0]=0;
  dfs2(0);
  cout<<ans<<endl;
  return 0;
}
  

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