import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Stream;

public class Main {

	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		MyInput in = new MyInput(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		TaskX solver = new TaskX();
		solver.solve(1, in, out);
		out.close();
	}

	static int INF = 1 << 30;
	static long LINF = 1L << 55;
	static int MOD = 1000000007;
	static int[] mh4 = { 0, -1, 1, 0 };
	static int[] mw4 = { -1, 0, 0, 1 };
	static int[] mh8 = { -1, -1, -1, 0, 0, 1, 1, 1 };
	static int[] mw8 = { -1, 0, 1, -1, 1, -1, 0, 1 };

	static class TaskX {

		int n, m;
		List<P>[] g;
		long[][][] cost;
		@SuppressWarnings("unchecked")
		public void solve(int testNumber, MyInput in, PrintWriter out) {

			n = in.nextInt(); m = in.nextInt();
			int[] u = new int[m], v = new int[m], s = new int[m];
			g = new ArrayList[n];
			g = Stream.generate(ArrayList::new).limit(n).toArray(List[]::new);

			// [初期コスト][偶奇][頂点] = コスト
			cost = new long[2][2][n];
			for (int i = 0; i < m; i++) {
				u[i] = in.nextInt()-1;
				v[i] = in.nextInt()-1;
				s[i] = in.nextInt();
				g[u[i]].add(new P(v[i], s[i]));
				g[v[i]].add(new P(u[i], s[i]));
			}

			fill(cost, LINF);
			dfs(0, 0, 0, 0);
			dfs(1, 0, 0, 1);

			// 奇数長の閉路があるので二部グラフではない場合
			if (cost[0][1][0] != LINF) {
				long ret = Math.abs(cost[0][0][0] - cost[0][1][0]);
				for (int x = 0; x < n; x++) {
					cost[0][0][x] = cost[0][1][x] = LINF;
				}

				// コストを (a+b)/2 として頂点のコストが 0 以下にならないことを確認
				dfs(0, 0, 0, ret / 2);
				for (int i = 0; i < n; i++) {
					if (Math.min(cost[0][0][i], cost[0][1][i]) <= 0) {
						out.println(0);
						return;
					}
				}
				out.println(1);

			} else {

				// 各頂点の値が正になるような初期値の範囲[L, R]
				long L = 1, R = LINF;
				for (int i = 1; i < n; i++) {
					int cur = (cost[0][0][i] == LINF ? 1 : 0);
					long diff = cost[1][cur][i] - cost[0][cur][i];
					if (diff == 1) L = Math.max(L, 1 - cost[0][cur][i]);
					if (diff == -1) R = Math.min(R, cost[0][cur][i] - 1);
				}

				out.println(Math.max(0, R - L + 1));
			}

		}

		void dfs(int id, int st, int cur, long v) {
			if (cost[id][st][cur] == LINF) {
				cost[id][st][cur] = v;
				for (P p : g[cur]) {
					dfs(id, st^1, p.t, p.c - v);
				}
			}
			if (cost[id][st][cur] != v) {
				System.out.println(0);
				System.exit(0);
			}
		}

		class P {
			int t;
			long c;

			public P(int t, long c) {
				super();
				this.t = t;
				this.c = c;
			}
		}
	}

	static void fill(long[][][] a, long v) {
		for (int i = 0; i < a.length; i++) {
			for (int j = 0; j < a[0].length; j++) {
				for (int k = 0; k < a[0][0].length; k++) {
					a[i][j][k] = v;
				}
			}
		}
	}

	static class MyInput {
		private final BufferedReader in;
		private static int pos;
		private static int readLen;
		private static final char[] buffer = new char[1024 * 8];
		private static char[] str = new char[500 * 8 * 2];
		private static boolean[] isDigit = new boolean[256];
		private static boolean[] isSpace = new boolean[256];
		private static boolean[] isLineSep = new boolean[256];

		static {
			for (int i = 0; i < 10; i++) {
				isDigit['0' + i] = true;
			}
			isDigit['-'] = true;
			isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
			isLineSep['\r'] = isLineSep['\n'] = true;
		}

		public MyInput(InputStream is) {
			in = new BufferedReader(new InputStreamReader(is));
		}

		public int read() {
			if (pos >= readLen) {
				pos = 0;
				try {
					readLen = in.read(buffer);
				} catch (IOException e) {
					throw new RuntimeException();
				}
				if (readLen <= 0) {
					throw new MyInput.EndOfFileRuntimeException();
				}
			}
			return buffer[pos++];
		}

		public int nextInt() {
			int len = 0;
			str[len++] = nextChar();
			len = reads(len, isSpace);
			int i = 0;
			int ret = 0;
			if (str[0] == '-') {
				i = 1;
			}
			for (; i < len; i++)
				ret = ret * 10 + str[i] - '0';
			if (str[0] == '-') {
				ret = -ret;
			}
			return ret;
		}

		public long nextLong() {
			int len = 0;
			str[len++] = nextChar();
			len = reads(len, isSpace);
			int i = 0;
			long ret = 0;
			if (str[0] == '-') {
				i = 1;
			}
			for (; i < len; i++)
				ret = ret * 10 + str[i] - '0';
			if (str[0] == '-') {
				ret = -ret;
			}
			return ret;
		}

		public char nextChar() {
			while (true) {
				final int c = read();
				if (!isSpace[c]) {
					return (char) c;
				}
			}
		}

		public String nextString() {
			return new String(nextChars());
		}

		public char[] nextChars() {
			int len = 0;
			str[len++] = nextChar();
			len = reads(len, isSpace);
			return Arrays.copyOf(str, len);
		}

		public char[][] next2DChars(int h, int w) {
			char[][] s = new char[h][w];
			for (int i = 0; i < h; i++) {
				s[i] = nextChars();
			}
			return s;
		}

		int reads(int len, boolean[] accept) {
			try {
				while (true) {
					final int c = read();
					if (accept[c]) {
						break;
					}
					if (str.length == len) {
						char[] rep = new char[str.length * 3 / 2];
						System.arraycopy(str, 0, rep, 0, str.length);
						str = rep;
					}
					str[len++] = (char) c;
				}
			} catch (MyInput.EndOfFileRuntimeException e) {
			}
			return len;
		}

		public int[] nextIntArray(final int n) {
			final int[] res = new int[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextInt();
			}
			return res;
		}

		public int[] nextIntArray1Index(final int n) {
			final int[] res = new int[n + 1];
			for (int i = 1; i < n + 1; i++) {
				res[i] = nextInt();
			}
			return res;
		}

		public int[] nextIntArrayDec(final int n) {
			final int[] res = new int[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextInt() - 1;
			}
			return res;
		}

		public long[] nextLongArray(final int n) {
			final long[] res = new long[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextLong();
			}
			return res;
		}

		public long[] nextLongArray1Index(final int n) {
			final long[] res = new long[n + 1];
			for (int i = 1; i < n + 1; i++) {
				res[i] = nextLong();
			}
			return res;
		}

		public long[] nextLongArrayDec(final int n) {
			final long[] res = new long[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextLong() - 1;
			}
			return res;
		}

		public double nextDouble() {
			return Double.parseDouble(nextString());
		}

		public double[] nextDoubleArray(int n) {
			double[] res = new double[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextDouble();
			}
			return res;
		}

		static class EndOfFileRuntimeException extends RuntimeException {
		}

	}

}


Measured memory_bytes: 74084