#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define pb push_back
#define sz(x) (int)(x.size())
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define vi vector<int>
#define vp vector<pii>
#define vvi vector<vi>
#define ykh mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count())
#define __lg(x) 63-__builtin_clzll(x)
#define pow2(x) (1LL<<x)
void __print(int x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef local
void CHECK();
void setio(){
freopen("/Users/iantsai/cpp/input.txt","r",stdin);
freopen("/Users/iantsai/cpp/output.txt","w",stdout);
}
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
void setio(){}
#define debug(x...)
#endif
#define TOI_is_so_de ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);setio();
const int mxn = 3e5 + 5;
inline char gc()
{
const static int SZ = 1 << 16;
static char buf[SZ], *p1, *p2;
if (p1 == p2 && (p2 = buf + fread(p1 = buf, 1, SZ, stdin), p1 == p2))
return -1;
return *p1++;
}
inline void rd() {}
template <typename T, typename... U>
inline void rd(T &x, U &...y)
{
x = 0;
bool f = 0;
char c = gc();
while (isdigit(c))
x = (x << 1) + (x << 3) + (c ^ 48), c = gc();
f && (x = -x), rd(y...);
}
template <typename T>
inline void prt(T x)
{
if (x > 9)
prt(x / 10);
putchar((x % 10) ^ 48);
}
vector<int>adj[mxn];
int n, m, l[mxn];
inline priority_queue<long long> dfs(int v, int pa){
priority_queue<long long>pq;
if(v > n){
pq.push(l[v]), pq.push(l[v]);
return pq;
}
for(auto u : adj[v]){
if(u == pa) continue;
auto pq2 = dfs(u, v);
if(sz(pq) < sz(pq2)) swap(pq, pq2);
while(sz(pq2)){
pq.push(pq2.top());
pq2.pop();
}
}
for(int i = 1; i < sz(adj[v]); i++){
pq.pop();
}
long long R = pq.top(); pq.pop();
long long L = pq.top(); pq.pop();
pq.push(l[v] + L), pq.push(l[v] + R);
return pq;
}
inline void solve(){
rd(n), rd(m);
long long sum = 0, prev = 0;
int slp = 1;
for(int i = 2; i <= n + m; i++){
int a;
rd(a), rd(l[i]);
sum += l[i];
adj[a].pb(i);
}
auto pq = dfs(1, 1);
vector<long long>vec;
while(sz(pq)){
vec.pb(pq.top());
pq.pop();
slp--;
}
while(sz(vec)){
sum += (long long)(vec.back() - prev) * slp;
prev = vec.back();
slp++;
vec.pop_back();
}
prt(sum);
}
signed main(){
TOI_is_so_de;
int t = 1;
//cin >> t;
while(t--){
solve();
}
#ifdef local
CHECK();
#endif
}
/*
input:
*/
#ifdef local
void CHECK(){
cerr << "\n[Time]: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
function<bool(string,string)> compareFiles = [](string p1, string p2)->bool {
std::ifstream file1(p1);
std::ifstream file2(p2);
if(!file1.is_open() || !file2.is_open()) return false;
std::string line1, line2;
while (getline(file1, line1) && getline(file2, line2)) {
if (line1 != line2)return false;
}
int cnta = 0, cntb = 0;
while(getline(file1,line1))cnta++;
while(getline(file2,line2))cntb++;
return cntb - cnta <= 1;
};
bool check = compareFiles("output.txt","expected.txt");
if(check) cerr<<"ACCEPTED\n";
else cerr<<"WRONG ANSWER!\n";
}
#else
#endif
