#include <bits/stdc++.h>
using namespace std;

#define INF_LL (int64)1e18
#define INF (int32)1e9
#define REP(i, n) for(int64 i = 0;i < (n);i++)
#define FOR(i, a, b) for(int64 i = (a);i < (b);i++)
#define all(x) x.begin(),x.end()
#define fs first
#define sc second

using int32 = int_fast32_t;
using uint32 = uint_fast32_t;
using int64 = int_fast64_t;
using uint64 = uint_fast64_t;
using PII = pair<int32, int32>;
using PLL = pair<int64, int64>;

const double eps = 1e-10;

template<typename A, typename B>inline void chmin(A &a, B b){if(a > b) a = b;}
template<typename A, typename B>inline void chmax(A &a, B b){if(a < b) a = b;}

template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value!=0>::type
fill_v(U &u,const V... v){u=U(v...);}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value==0>::type
fill_v(U &u,const V... v){
  for(auto &e:u) fill_v<T>(e,v...);
}

template<::std::uint_fast64_t mod>
class ModInt{
private:
	using value_type = ::std::uint_fast64_t;
	value_type n;
public:
	ModInt() : n(0) {}
	ModInt(value_type n_) : n(n_ % mod) {}
	ModInt(const ModInt& m) : n(m.n) {}

	template<typename T>
	explicit operator T() const { return static_cast<T>(n); }
	value_type get() const { return n; }

	friend ::std::ostream& operator<<(::std::ostream &os, const ModInt<mod> &a) {
		return os << a.n;
	}

	friend ::std::istream& operator>>(::std::istream &is, ModInt<mod> &a) {
		value_type x;
		is >> x;
		a = ModInt<mod>(x);
		return is;
	}

	bool operator==(const ModInt& m) const { return n == m.n; }
	bool operator!=(const ModInt& m) const { return n != m.n; }
	ModInt& operator*=(const ModInt& m){ n = n * m.n % mod; return *this; }

	ModInt pow(value_type b) const{
		ModInt ans = 1, m = ModInt(*this);
		while(b){
			if(b & 1) ans *= m;
			m *= m;
			b >>= 1;
		}
		return ans;
	}

	ModInt inv() const { return (*this).pow(mod-2); }
	ModInt& operator+=(const ModInt& m){ n += m.n; n = (n < mod ? n : n - mod); return *this; }
	ModInt& operator-=(const ModInt& m){ n += mod - m.n; n = (n < mod ? n : n - mod); return *this; }
	ModInt& operator/=(const ModInt& m){ *this *= m.inv(); return *this; }
	ModInt operator+(const ModInt& m) const { return ModInt(*this) += m; }
	ModInt operator-(const ModInt& m) const { return ModInt(*this) -= m; }
	ModInt operator*(const ModInt& m) const { return ModInt(*this) *= m; }
	ModInt operator/(const ModInt& m) const { return ModInt(*this) /= m; }
	ModInt& operator++(){ n += 1; return *this; }
	ModInt& operator--(){ n -= 1; return *this; }
	ModInt operator++(int){
		ModInt old(n);
		n += 1;
		return old;
	}
	ModInt operator--(int){
		ModInt old(n);
		n -= 1;
		return old;
	}
	ModInt operator-() const { return ModInt(mod-n); }
};

template<::std::size_t size, ::std::uint_fast64_t mod=1000000007>
class Factorial{
private:
	using value_type = ModInt<mod>;
	::std::vector<value_type> fact, inv;
public:
	Factorial() : fact(size+1, 1), inv(size+1, 1){
		for(::std::size_t i = 1; i <= size; ++i){
			fact[i] = fact[i-1] * value_type(i);
			inv[i] = fact[i].inv();
		}
	}

	value_type comb(::std::int64_t a, ::std::int64_t b){
		assert(a >= b);
		assert(b >= 0);
		return fact[a]*inv[b]*inv[a-b];
	}

	value_type& operator[](::std::size_t k){ return fact[k]; }
};

const int64 mod = 1e9+7;
using Mint = ModInt<mod>;
Factorial<112345> f;

int64 N, M;
vector<PLL> G[112345];
vector<PLL> info[2]; // {sgn x, +a}

void dfs(int64 v, int64 t, int64 p) {
	for (auto u : G[v]) {
		if (u.sc == p) continue;
		PLL nxt = PLL(info[t][v].fs^1, u.fs-info[t][v].sc);
		if (info[nxt.fs][u.sc] == PLL(-1, -1)) {
			info[nxt.fs][u.sc] = nxt;
			dfs(u.sc, nxt.fs, v);
		} else {
			if (info[nxt.fs][u.sc] != nxt) {
				cout << 0 << endl;
				exit(0);
			}
		}
	}
}

vector<int64> memo;
bool ok(int64 v, int64 p, int64 x) {
	memo[v] = 1;
	bool ret = 1;
	for (auto u : G[v]) {
		if (memo[u.sc] != -1) continue;
		if (u.fs - x <= 0) return 0;
		ret &= ok(u.sc, v, u.fs-x);	
	}
	return ret;
}

int main(void) {
	cin >> N >> M;
	info[0].resize(N, PLL(-1, -1));
	info[1].resize(N, PLL(-1, -1));
	memo.resize(N, -1);
	REP(i, M) {
		int64 u, v, s;
		cin >> u >> v >> s; u--; v--;
		G[u].emplace_back(s, v);
		G[v].emplace_back(s, u);
	}
	info[0][0] = PLL(0, 0);
	dfs(0, 0, -1);
	int64 res[2] = {INF_LL, INF_LL};
	REP(i, N) {
		if (info[0][i] != PLL(-1, -1) && info[1][i] != PLL(-1, -1)) {
			if (ok(i, 0, (info[0][i].sc+info[1][i].sc)/2)) {
				cout << 1 << endl;
				return 0;
			} else {
				cout << 0 << endl;
				return 0;
			}
		} else {
			if (info[0][i] != PLL(-1, -1)) {
				chmin(res[0], info[0][i].sc);
			} else {
				chmin(res[1], info[1][i].sc);
			}
		}
	}
	cout << max((int64)0, res[1]+min((int64)1, res[0])-1) << endl;
}


Measured memory_bytes: 22912