package adv2020;

import java.io.*;
import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Queue;

public class Day17_3 {
	InputStream is;
	FastWriter out;

	String INPUT = "";



	public void solve()
	{
		int T = ni();
		int n = ni(), m = ni();
		int[] from = new int[m];
		int[] to = new int[m];
		int[] ws = new int[m];
		for(int i = 0;i < m;i++){
		    from[i] = ni()-1;
		    to[i] = ni()-1;
		    ws[i] = ni();
		}
		int[][][] g = T == 0 ? packWU(n, from, to, ws) : packWD(n, from, to, ws);
		long ans = Long.MAX_VALUE / 2;
		for(int cut = 0;cut < m;cut++){
			long[] td = new long[n];
			Arrays.fill(td, Long.MAX_VALUE / 2);
			RadixHeapL q = new RadixHeapL(50, n);
			q.add(to[cut], 0);
			td[to[cut]] = 0;

			while (q.size > 0) {
				int cur = q.argmin();

				for (int[] e : g[cur]) {
					if(cur == from[cut] && e[0] == to[cut])continue;
					if(e[0] == from[cut] && cur == to[cut])continue;
					int next = e[0];
					long nd = td[cur] + e[1];
					if (nd < td[next]) {
						td[next] = nd;
						q.update(next, nd);
					}
				}
				q.remove(cur);
			}
			ans = Math.min(ans, td[from[cut]] + ws[cut]);
		}
		out.println(ans == Long.MAX_VALUE / 2 ? -1 : ans);
	}

	public class RadixHeapL {
		public long[][] vals; // (clus,index) -> value (dirty)
		public int[][] keys; // (clus,index) -> key (dirty)
		public int[] imapclus; // key -> clus
		public int[] imapind; // key -> index
		public int[] ps; // size of clus
		public long min;
		public int size;

		public RadixHeapL(int numdigit, int lim)
		{
			min = 0;
			size = 0;
			vals = new long[numdigit][1];
			ps = new int[numdigit];

			keys = new int[numdigit][1];
			imapclus = new int[lim];
			Arrays.fill(imapclus, -1);
			imapind = new int[lim];
			Arrays.fill(imapind, -1);
		}

		// no checking add
		public void add(int key, long x)
		{
			if(x < min)throw new RuntimeException("x:" + x + ", min:" + min);
			if(size == 0)min = x;
			allocate(key, x);
			size++;
		}

		public boolean contains(int key)
		{
			return imapclus[key] != -1;
		}

		public boolean remove(int key)
		{
			int clus = imapclus[key];
			int ind = imapind[key];
			if(clus == -1)return false; // not found

			imapclus[key] = -1;
			imapind[key] = -1;
			if(ind < ps[clus] - 1){
				// move tail one to the deleted space
				vals[clus][ind] = vals[clus][ps[clus]-1];
				keys[clus][ind] = keys[clus][ps[clus]-1];
				imapind[keys[clus][ind]] = ind;
			}
			ps[clus]--;
			size--;

			if(clus == 0 && ps[clus] == 0)redistribute();
			return true;
		}

		public void update(int key, long x)
		{
			int clus = imapclus[key];
			int ind = imapind[key];
			if(clus != -1){
				imapclus[key] = -1;
				imapind[key] = -1;
				if(ind < ps[clus] - 1){
					// move tail one to the deleted space
					vals[clus][ind] = vals[clus][ps[clus]-1];
					keys[clus][ind] = keys[clus][ps[clus]-1];
					imapind[keys[clus][ind]] = ind;
				}
				ps[clus]--;
				size--;
			}

			if(x < min)throw new RuntimeException("x:" + x + ", min:" + min);
			allocate(key, x);
			if(ps[0] == 0)redistribute();
			size++;
		}

		public int argmin() { return ps[0]-1 >= 0 ? keys[0][ps[0]-1] : -1; }

		public long poll()
		{
			long ret = min;
			if(size > 0){
				size--;
				int key = keys[0][ps[0]-1];
				imapclus[key] = -1;
				imapind[key] = -1;
				if(--ps[0] == 0)redistribute();
			}
			return ret;
		}

		private void allocate(int key, long x)
		{
			int ind = 64-Long.numberOfLeadingZeros(min^x);
			if(ps[ind] == vals[ind].length){
				vals[ind] = Arrays.copyOf(vals[ind], ps[ind]*2);
				keys[ind] = Arrays.copyOf(keys[ind], ps[ind]*2);
			}
			vals[ind][ps[ind]] = x;
			keys[ind][ps[ind]] = key;
			imapclus[key] = ind;
			imapind[key] = ps[ind];
			ps[ind]++;
		}

		private void redistribute()
		{
			min = 0;
			for(int i = 0;i < vals.length;i++){
				if(ps[i] > 0){
					// search min
					int arg = 0;
					for(int j = 0;j < ps[i];j++){
						if(vals[i][j] < vals[i][arg])arg = j;
					}
					min = vals[i][arg];

					// reallocate
					for(int j = 0;j < ps[i];j++){
						allocate(keys[i][j], vals[i][j]);
					}
					ps[i] = 0;
					break;
				}
			}
		}

		public String toString()
		{
			StringBuilder sb = new StringBuilder();
			sb.append("min:" + min + "\n");
			sb.append("size:" + size + "\n");
			for(int i = 0;i < vals.length;i++){
				if(ps[i] == 0)continue;
				sb.append(i + "V:" + Arrays.toString(Arrays.copyOf(vals[i], ps[i])) + "\n");
				sb.append(i + "K:" + Arrays.toString(Arrays.copyOf(keys[i], ps[i])) + "\n");
			}
			return sb.toString();
		}
	}

	public static int[][][] packWD(int n, int[] from, int[] to, int[] w) {
		return packWD(n, from, to, w, from.length);
	}

	public static int[][][] packWD(int n, int[] from, int[] to, int[] w, int sup) {
		int[][][] g = new int[n][][];
		int[] p = new int[n];
		for (int i = 0; i < sup; i++) p[from[i]]++;
		for (int i = 0; i < n; i++) g[i] = new int[p[i]][2];
		for (int i = 0; i < sup; i++) {
			--p[from[i]];
			g[from[i]][p[from[i]]][0] = to[i];
			g[from[i]][p[from[i]]][1] = w[i];
		}
		return g;
	}

	public static int[][][] packWU(int n, int[] from, int[] to, int[] w) {
		return packWU(n, from, to, w, from.length);
	}

	public static int[][][] packWU(int n, int[] from, int[] to, int[] w, int sup) {
		int[][][] g = new int[n][][];
		int[] p = new int[n];
		for (int i = 0; i < sup; i++) p[from[i]]++;
		for (int i = 0; i < sup; i++) p[to[i]]++;
		for (int i = 0; i < n; i++) g[i] = new int[p[i]][2];
		for (int i = 0; i < sup; i++) {
			--p[from[i]];
			g[from[i]][p[from[i]]][0] = to[i];
			g[from[i]][p[from[i]]][1] = w[i];
			--p[to[i]];
			g[to[i]][p[to[i]]][0] = from[i];
			g[to[i]][p[to[i]]][1] = w[i];
		}
		return g;
	}


	public static void main(String[] args) {
		new Day17_3().run();
	}

	public void run()
	{
		long S = System.currentTimeMillis();
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new FastWriter(System.out);

		solve();
		out.flush();
		long G = System.currentTimeMillis();
		tr(G-S+"ms");
		//		Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){
		//			@Override
		//			public void run() {
		//				long s = System.currentTimeMillis();
		//				solve();
		//				out.flush();
		//				if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
		//			}
		//		};
		//		t.start();
		//		t.join();
	}

	private boolean eof()
	{
		if(lenbuf == -1)return true;
		int lptr = ptrbuf;
		while(lptr < lenbuf)if(!isSpaceChar(inbuf[lptr++]))return false;

		try {
			is.mark(1000);
			while(true){
				int b = is.read();
				if(b == -1){
					is.reset();
					return true;
				}else if(!isSpaceChar(b)){
					is.reset();
					return false;
				}
			}
		} catch (IOException e) {
			return true;
		}
	}

	private final byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;

	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	//	private boolean isSpaceChar(int c) { return !(c >= 32 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }

	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }

	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}

	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}

	private long[] nal(int n)
	{
		long[] a = new long[n];
		for(int i = 0;i < n;i++)a[i] = nl();
		return a;
	}

	private int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}

		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}

		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	public static class FastWriter
	{
		private static final int BUF_SIZE = 1<<13;
		private final byte[] buf = new byte[BUF_SIZE];
		private final OutputStream out;
		private int ptr = 0;

		private FastWriter(){out = null;}

		public FastWriter(OutputStream os)
		{
			this.out = os;
		}

		public FastWriter(String path)
		{
			try {
				this.out = new FileOutputStream(path);
			} catch (FileNotFoundException e) {
				throw new RuntimeException("FastWriter");
			}
		}

		public FastWriter write(byte b)
		{
			buf[ptr++] = b;
			if(ptr == BUF_SIZE)innerflush();
			return this;
		}

		public FastWriter write(char c)
		{
			return write((byte)c);
		}

		public FastWriter write(char[] s)
		{
			for(char c : s){
				buf[ptr++] = (byte)c;
				if(ptr == BUF_SIZE)innerflush();
			}
			return this;
		}

		public FastWriter write(String s)
		{
			s.chars().forEach(c -> {
				buf[ptr++] = (byte)c;
				if(ptr == BUF_SIZE)innerflush();
			});
			return this;
		}

		private static int countDigits(int l) {
			if (l >= 1000000000) return 10;
			if (l >= 100000000) return 9;
			if (l >= 10000000) return 8;
			if (l >= 1000000) return 7;
			if (l >= 100000) return 6;
			if (l >= 10000) return 5;
			if (l >= 1000) return 4;
			if (l >= 100) return 3;
			if (l >= 10) return 2;
			return 1;
		}

		public FastWriter write(int x)
		{
			if(x == Integer.MIN_VALUE){
				return write((long)x);
			}
			if(ptr + 12 >= BUF_SIZE)innerflush();
			if(x < 0){
				write((byte)'-');
				x = -x;
			}
			int d = countDigits(x);
			for(int i = ptr + d - 1;i >= ptr;i--){
				buf[i] = (byte)('0'+x%10);
				x /= 10;
			}
			ptr += d;
			return this;
		}

		private static int countDigits(long l) {
			if (l >= 1000000000000000000L) return 19;
			if (l >= 100000000000000000L) return 18;
			if (l >= 10000000000000000L) return 17;
			if (l >= 1000000000000000L) return 16;
			if (l >= 100000000000000L) return 15;
			if (l >= 10000000000000L) return 14;
			if (l >= 1000000000000L) return 13;
			if (l >= 100000000000L) return 12;
			if (l >= 10000000000L) return 11;
			if (l >= 1000000000L) return 10;
			if (l >= 100000000L) return 9;
			if (l >= 10000000L) return 8;
			if (l >= 1000000L) return 7;
			if (l >= 100000L) return 6;
			if (l >= 10000L) return 5;
			if (l >= 1000L) return 4;
			if (l >= 100L) return 3;
			if (l >= 10L) return 2;
			return 1;
		}

		public FastWriter write(long x)
		{
			if(x == Long.MIN_VALUE){
				return write("" + x);
			}
			if(ptr + 21 >= BUF_SIZE)innerflush();
			if(x < 0){
				write((byte)'-');
				x = -x;
			}
			int d = countDigits(x);
			for(int i = ptr + d - 1;i >= ptr;i--){
				buf[i] = (byte)('0'+x%10);
				x /= 10;
			}
			ptr += d;
			return this;
		}

		public FastWriter write(double x, int precision)
		{
			if(x < 0){
				write('-');
				x = -x;
			}
			x += Math.pow(10, -precision)/2;
			//		if(x < 0){ x = 0; }
			write((long)x).write(".");
			x -= (long)x;
			for(int i = 0;i < precision;i++){
				x *= 10;
				write((char)('0'+(int)x));
				x -= (int)x;
			}
			return this;
		}

		public FastWriter writeln(char c){
			return write(c).writeln();
		}

		public FastWriter writeln(int x){
			return write(x).writeln();
		}

		public FastWriter writeln(long x){
			return write(x).writeln();
		}

		public FastWriter writeln(double x, int precision){
			return write(x, precision).writeln();
		}

		public FastWriter write(int... xs)
		{
			boolean first = true;
			for(int x : xs) {
				if (!first) write(' ');
				first = false;
				write(x);
			}
			return this;
		}

		public FastWriter write(long... xs)
		{
			boolean first = true;
			for(long x : xs) {
				if (!first) write(' ');
				first = false;
				write(x);
			}
			return this;
		}

		public FastWriter writeln()
		{
			return write((byte)'\n');
		}

		public FastWriter writeln(int... xs)
		{
			return write(xs).writeln();
		}

		public FastWriter writeln(long... xs)
		{
			return write(xs).writeln();
		}

		public FastWriter writeln(char[] line)
		{
			return write(line).writeln();
		}

		public FastWriter writeln(char[]... map)
		{
			for(char[] line : map)write(line).writeln();
			return this;
		}

		public FastWriter writeln(String s)
		{
			return write(s).writeln();
		}

		private void innerflush()
		{
			try {
				out.write(buf, 0, ptr);
				ptr = 0;
			} catch (IOException e) {
				throw new RuntimeException("innerflush");
			}
		}

		public void flush()
		{
			innerflush();
			try {
				out.flush();
			} catch (IOException e) {
				throw new RuntimeException("flush");
			}
		}

		public FastWriter print(byte b) { return write(b); }
		public FastWriter print(char c) { return write(c); }
		public FastWriter print(char[] s) { return write(s); }
		public FastWriter print(String s) { return write(s); }
		public FastWriter print(int x) { return write(x); }
		public FastWriter print(long x) { return write(x); }
		public FastWriter print(double x, int precision) { return write(x, precision); }
		public FastWriter println(char c){ return writeln(c); }
		public FastWriter println(int x){ return writeln(x); }
		public FastWriter println(long x){ return writeln(x); }
		public FastWriter println(double x, int precision){ return writeln(x, precision); }
		public FastWriter print(int... xs) { return write(xs); }
		public FastWriter print(long... xs) { return write(xs); }
		public FastWriter println(int... xs) { return writeln(xs); }
		public FastWriter println(long... xs) { return writeln(xs); }
		public FastWriter println(char[] line) { return writeln(line); }
		public FastWriter println(char[]... map) { return writeln(map); }
		public FastWriter println(String s) { return writeln(s); }
		public FastWriter println() { return writeln(); }
	}

	public static void trnz(int... o)
	{
		for(int i = 0;i < o.length;i++)if(o[i] != 0)System.out.print(i+":"+o[i]+" ");
		System.out.println();
	}

	// print ids which are 1
	public static void trt(long... o)
	{
		Queue<Integer> stands = new ArrayDeque<>();
		for(int i = 0;i < o.length;i++){
			for(long x = o[i];x != 0;x &= x-1)stands.add(i<<6|Long.numberOfTrailingZeros(x));
		}
		System.out.println(stands);
	}

	public static void tf(boolean... r)
	{
		for(boolean x : r)System.out.print(x?'#':'.');
		System.out.println();
	}

	public static void tf(boolean[]... b)
	{
		for(boolean[] r : b) {
			for(boolean x : r)System.out.print(x?'#':'.');
			System.out.println();
		}
		System.out.println();
	}

	public void tf(long[]... b)
	{
		if(INPUT.length() != 0) {
			for (long[] r : b) {
				for (long x : r) {
					for (int i = 0; i < 64; i++) {
						System.out.print(x << ~i < 0 ? '#' : '.');
					}
				}
				System.out.println();
			}
			System.out.println();
		}
	}

	public void tf(long... b)
	{
		if(INPUT.length() != 0) {
			for (long x : b) {
				for (int i = 0; i < 64; i++) {
					System.out.print(x << ~i < 0 ? '#' : '.');
				}
			}
			System.out.println();
		}
	}

	private void tr(Object... o) { if(INPUT.length() != 0)System.out.println(Arrays.deepToString(o)); }
}