// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(st, itr) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define vrep(v, i) for(int i = 0; i < (v).size(); i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
#define dump(a, n) for(int i = 0; i < n; i++)cout << a[i] << "\n "[i + 1 != n];
#define dump2(a, n, m) for(int i = 0; i < n; i++)for(int j = 0; j < m; j++)cout << a[i][j] << "\n "[j + 1 != m];
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}

vector<pair<int, ll>> edge[200001];
bool used[200001];
int sign[200001];
ll coef[200001];

void dfs(int i){
  used[i] = true;
  for(auto e: edge[i]){
    int to = e.first;
    ll s = e.second;
    if(used[to])continue;
    sign[to] = - sign[i];
    coef[to] = s - coef[i];
    dfs(to);
  }
}

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  rep(i, m){
    int u, v;
    ll s;
    cin >> u >> v >> s, u--, v--;
    edge[u].pb(mk(v, s));
    edge[v].pb(mk(u, s));
  }
  used[0] = true;
  sign[0] = 1;
  coef[0] = 0;
  dfs(0);
  //dump(sign, n);
  //dump(coef, n);
  set<ll> st;
  rep(i, n){
    for(auto e: edge[i]){
      int to = e.FI;
      ll s = e.SE;
      if(sign[i] == sign[to]){
        if(sign[i] > 0){
          if(s - coef[i] - coef[to] <= 0 || (s - coef[i] - coef[to]) % 2 == 1){
            cout << 0 << endl;
            return 0;
          }
          st.insert((s - coef[i] - coef[to]) / 2);
        }else{
          if(coef[i] + coef[to] - s <= 0 || (coef[i] + coef[to] - s) % 2 == 1){
            cout << 0 << endl;
            return 0;
          }
          st.insert((coef[i] + coef[to] - s) / 2);
        }
      }else{
        if(coef[i] + coef[to] != s){
          cout << 0 << endl;
          return 0;
        }
      }
    }
  }
  if(sz(st)){
    if(sz(st) > 1)cout << 0 << endl;
    else {
      rep(i, n){
        ll cos = coef[i] + sign[i] * (*st.begin());
        for(auto e: edge[i]){
          if(cos <= 0 || cos >= e.SE){
            cout << 0 << endl;
            return 0;
          }
        }
      }
      cout << 1 << endl;
    }
    return 0;
  }
  ll mini = 1, maxi = inf;
  rep(i, n){
    for(auto e: edge[i]){
      ll s = e.SE;
      if(sign[i] == 1){
        mini = max(mini, 1 - coef[i]);
        maxi = min(maxi, s - coef[i] - 1);
      }else{
        mini = max(mini, coef[i] - s + 1);
        maxi = min(maxi, coef[i] - 1);
      }
    }
  }
  cout << max(0LL, maxi - mini + 1) << endl;
  return 0;
}


Measured memory_bytes: 14976