import java.util.*; import java.io.*; public class Main { static int n; static ArrayList[] edges; static int[] cnt; static long ret = 0; public static void main(String[] args){ FastScanner scanner = new FastScanner(); n = scanner.nextInt(); int[] u = new int[n]; int[] v = new int[n]; int[] w = new int[n]; edges = new ArrayList[n]; cnt = new int[n]; for(int i = 0; i < n; i++){ edges[i] = new ArrayList(); } for(int i = 0; i < n-1; i++){ u[i] = scanner.nextInt()-1; v[i] = scanner.nextInt()-1; w[i] = scanner.nextInt(); edges[u[i]].add(new Edge(v[i],w[i])); edges[v[i]].add(new Edge(u[i],w[i])); } dfs(0,-1); System.out.println(ret*2); } public static int dfs(int i, int parent){ cnt[i] = 1; int r = 0; for(Edge e : edges[i]){ if(e.to == parent){ r = e.cost; }else{ cnt[i] += dfs(e.to,i); } } ret += r*cnt[i]*(n-cnt[i]); return cnt[i]; } public static class Edge{ int to; int cost; Edge(int to, int cost){ this.to = to; this.cost = cost; } } private static class FastScanner { private final InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; private boolean hasNextByte() { if (ptr < buflen) { return true; }else{ ptr = 0; try { buflen = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (buflen <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;} private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;} public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();} public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while(isPrintableChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); long n = 0; boolean minus = false; int b = readByte(); if (b == '-') { minus = true; b = readByte(); } if (b < '0' || '9' < b) { throw new NumberFormatException(); } while(true){ if ('0' <= b && b <= '9') { n *= 10; n += b - '0'; }else if(b == -1 || !isPrintableChar(b)){ return minus ? -n : n; }else{ throw new NumberFormatException(); } b = readByte(); } } public int nextInt() { long nl = nextLong(); if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException(); return (int) nl; } public double nextDouble() { return Double.parseDouble(next());} } }