func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, t1, t2, t3, t4, t5, dif, yes, rep, cnt[1005], last[1005],       ans[1005][1005], ma[1005][1005];   vector<int> nod, re, v[1005];   vector<pair<int, int> > path, more;   vector<pair<pair<int, int>, int> > sol;   bool vis[1005];   pair<int, int> pl, pr;   bool ok;   void clr() {     for (int i = 1; i <= n; i++) vis[i] = 0;     return;   }   int any(int mo) {     vis[mo] = 1;     if (v[mo].size() == 1)       return mo;     else {       for (int i = 0; i < v[mo].size(); i++) {         if (!vis[v[mo][i]]) {           return any(v[mo][i]);         }       }     }   }   pair<int, int> exp(int mo) {     clr();     vis[t4] = 1, vis[t5] = 1;     vector<int> ret;     for (int i = 0; i < v[mo].size(); i++) {       if (v[mo][i] != t4 && v[mo][i] != t5) {         ret.push_back(any(v[mo][i]));         if (ret.size() > 1) {           return make_pair(ret[0], ret[1]);         }       }     }   }   void dfs(int from, int to, int val) {     ok = 0;     vis[from] = 1;     if (from == to) {       ok = 1, yes = from;       return;     }     for (int i = 0; i < v[from].size(); i++) {       if (!vis[v[from][i]] && !ok) {         dfs(v[from][i], to, val);       }     }     if (ok) {       ma[from][yes] += val;       ma[yes][from] += val;       yes = from;       return;     }   }   int main() {     cin >> n;     for (int i = 0; i < n - 1; i++) {       cin >> t1 >> t2 >> t3;       path.push_back(make_pair(t1, t2));       cnt[t1]++, cnt[t2]++;       last[t1] = t3, last[t2] = t3;       v[t1].push_back(t2);       v[t2].push_back(t1);       ans[t1][t2] = t3;     }     for (int i = 1; i <= n; i++) {       if (cnt[i] == 2) {         cout <<  NO  << endl;         return 0;       }       if (cnt[i] == 1 && last[i] != 0) {         nod.push_back(i);       }     }     for (int i = 0; i < path.size(); i++) {       if (cnt[path[i].first] > 1 && cnt[path[i].second] > 1) {         more.push_back(path[i]);       }     }     sort(nod.begin(), nod.end());     while (nod.size() > 1) {       sol.push_back(make_pair(make_pair(nod[0], nod[1]), last[nod[0]]));       clr();       dfs(nod[0], nod[1], last[nod[0]]);       last[nod[1]] -= last[nod[0]];       if (re.size() < 2) re.push_back(nod[0]);       nod.erase(nod.begin());     }     if (nod.size() == 1 && n > 2) {       sol.push_back(make_pair(make_pair(re[1], nod[0]), last[nod[0]] / 2));       clr();       dfs(re[1], nod[0], last[nod[0]] / 2);       sol.push_back(make_pair(make_pair(re[0], re[1]), last[nod[0]] / -2));       clr();       dfs(re[0], re[1], last[nod[0]] / -2);       sol.push_back(make_pair(make_pair(re[0], nod[0]), last[nod[0]] / 2));       clr();       dfs(re[0], nod[0], last[nod[0]] / 2);     }     for (int i = 0; i < more.size(); i++) {       t4 = more[i].first, t5 = more[i].second;       if (ma[t4][t5] != ans[t4][t5]) {         pl = exp(t4), pr = exp(t5), dif = ans[t4][t5] - ma[t4][t5];         sol.push_back(make_pair(make_pair(pl.first, pr.first), dif / 2));         sol.push_back(make_pair(make_pair(pl.second, pr.second), dif / 2));         sol.push_back(make_pair(make_pair(pl.first, pl.second), dif / -2));         sol.push_back(make_pair(make_pair(pr.first, pr.second), dif / -2));       }     }     cout <<  YES  << endl << sol.size() << endl;     for (int i = 0; i < sol.size(); i++) {       cout << sol[i].first.first <<     << sol[i].first.second <<                << sol[i].second << endl;     }   }   