import java.util.*;
import java.io.*;

public class Main {
	static int n;
	static ArrayList<Edge>[] 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<Edge>();
		}
		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*2L);
	}
	public static long 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 += 1L*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());}
	}
}