#include <algorithm>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

#define MOD 1000000007
#define MOD2 998244353
#define int long long
#define double long double
#define EPS 1e-9
//#define PI 3.14159265358979

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

using namespace std;

template < typename T >
ostream &operator<<(ostream &os, const vector< T > &A) {
	for (int i = 0; i < A.size(); i++)
		os << A[i] << " ";
	os << endl;
	return os;
}
template <>
ostream &operator<<(ostream &os, const vector< vector< int > > &A) {
	int N = A.size();
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < A[i].size(); j++)
			os << A[i][j] << " ";
		os << endl;
	}
	return os;
}
template < typename T, typename U >
ostream &operator<<(ostream &os, const pair< T, U > &p) {
	os << "(" << p.first << "," << p.second << ")";
	return os;
}

typedef pair< int, int > pii;
typedef long long ll;

struct edge {
	int from, to, d, c, i;
	edge(int _from = 0, int _to = 0, int _d = 0, int _c = 0) {
		from = _from;
		to = _to;
		d = _d;
		c = _c;
	}
	bool operator<(const edge &rhs) const {
		return (d == rhs.d) ? (c < rhs.c) : (d < rhs.d);
	}
};
struct aabb {
	int x1, y1, x2, y2;
	aabb(int x1, int y1, int x2, int y2) : x1(x1), y1(y1), x2(x2), y2(y2) {}
};

typedef vector< edge > edges;
typedef vector< edges > graph;
struct flow {
	int to, cap, rev, cost;
	flow(int to = 0, int cap = 0, int rev = 0, int cost = 0) : to(to), cap(cap), rev(rev), cost(cost) {}
};
typedef vector< vector< flow > > flows;

const int di[4] = {0, -1, 0, 1};
const int dj[4] = {-1, 0, 1, 0};
const int ci[5] = {0, 0, -1, 0, 1};
const int cj[5] = {0, -1, 0, 1, 0};
const ll LINF = LLONG_MAX / 2;
const int INF = INT_MAX / 2;
const double PI = acos(-1);

int pow2(int n) { return 1LL << n; }
template < typename T, typename U >
bool chmin(T &x, const U &y) {
	if (x > y) {
		x = y;
		return true;
	}
	return false;
}
template < typename T, typename U >
bool chmax(T &x, const U &y) {
	if (x < y) {
		x = y;
		return true;
	}
	return false;
}

template < typename A, size_t N, typename T >
void Fill(A (&array)[N], const T &val) {
	fill((T *)array, (T *)(array + N), val);
}
struct initializer {
	initializer() {
		cout << fixed << setprecision(20);
	}
};
initializer _____;

int N, M, K, T, Q, H, W;
signed main() {
	cin >> N >> M;
	graph G(N);
	rep(i, M) {
		int u, v, s;
		cin >> u >> v >> s;
		--u;
		--v;
		G[u].emplace_back(u, v, s);
		G[v].emplace_back(v, u, s);
	}
	//1 gusu cycle&mujun
	//2 kisu cycle&warikirenai
	//3 kisu cycle&warikiri
	int j, l; //j:index l:val
	//0 cycle nashi or gusu&mujunnashi
	vector< int > val(N, -LINF);
	vector< int > label(N, 0);
	auto f1 = [&](auto &&f1, int x, int v, int d) -> int {
		val[x] = v;
		label[x] = d;
		for (auto &e : G[x]) {
			if (val[e.to] != -LINF) {
				if (label[x] == label[e.to]) {
					int v2 = v + e.d * d - val[e.to];
					v2 *= d;
					if (v2 <= 0 || (v2 & 1))
						return 2;
					j = e.to;
					l = v2 / 2;
					return 3;
				} else {
					int v2 = v + e.d * d - val[e.to];
					if (v2 != 0)
						return 1;
				}
			} else {
				int res = f1(f1, e.to, v + d * e.d, -d);
				if (res != 0)
					return res;
			}
		}
		return 0;
	};

	val[0] = 0;
	int res = f1(f1, 0, 0, 1);
	//cerr << res << endl;
	if (res == 1 || res == 2) {
		cout << 0 << endl;
		return 0;
	}
	if (res == 3) {
		vector< int > val(N, -1);
		val[j] = l;
		//cerr << val;
		auto f2 = [&](auto &&f2, int x) -> int {
			for (auto &e : G[x]) {
				if (val[e.to] != -1) {
					if (val[x] + val[e.to] != e.d)
						return 0;
					continue;
				}
				val[e.to] = e.d - val[x];
				if (val[e.to] <= 0)
					return 0;
				if (f2(f2, e.to) == 0)
					return 0;
			}
			return 1;
		};
		cout << f2(f2, j) << endl;
		return 0;
	}
	vector< int > L(N, -LINF), R(N, LINF);
	val.assign(N, -1);
	val[0] = 1;
	auto f3 = [&](auto &&f3, int x) -> void {
		for (auto &e : G[x]) {
			if (val[e.to] != -1) {
				continue;
			}
			val[e.to] = e.d - val[x];
			f3(f3, e.to);
		}
	};
	f3(f3, 0);
	l = 1;
	int r = LINF;
	rep(i, N) if (i != 0) {
		if (label[i] == label[0]) {
			chmax(l, -val[i] + 1 + 1);
		} else {
			chmin(r, val[i]);
		}
	}
	//cerr << l << r << endl;
	//cerr << val;
	cout << max(r - l + 1, 0LL) << endl;
	return 0;
}

Measured memory_bytes: 24752