#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <functional>
#include <set>
#include <ctime>
#include <random>
#include <chrono>
#include <cassert>
#include <stack>
#include <tuple>
#include <utility>
using namespace std;

namespace {
  using Integer = long long; //__int128;
  template<class T, class S> istream& operator >> (istream& is, pair<T,S>& p){return is >> p.first >> p.second;}
  template<class T> istream& operator >> (istream& is, vector<T>& vec){for(T& val: vec) is >> val; return is;}
  template<class T> istream& operator ,  (istream& is, T& val){ return is >> val;}
  template<class T, class S> ostream& operator << (ostream& os, const pair<T,S>& p){return os << p.first << " " << p.second;}
  template<class T> ostream& operator << (ostream& os, const vector<T>& vec){for(size_t i=0; i<vec.size(); i++) os << vec[i] << (i==vec.size()-1?"":" "); return os;}
  template<class T> ostream& operator ,  (ostream& os, const T& val){ return os << " " << val;}

  template<class H> void print(const H& head){ cout << head; }
  template<class H, class ... T> void print(const H& head, const T& ... tail){ cout << head << " "; print(tail...); }
  template<class ... T> void println(const T& ... values){ print(values...); cout << endl; }

  template<class H> void eprint(const H& head){ cerr << head; }
  template<class H, class ... T> void eprint(const H& head, const T& ... tail){ cerr << head << " "; eprint(tail...); }
  template<class ... T> void eprintln(const T& ... values){ eprint(values...); cerr << endl; }

  class range{ Integer start_, end_, step_; public: struct range_iterator{ Integer val, step_; range_iterator(Integer v, Integer step) : val(v), step_(step) {} Integer operator * (){return val;} void operator ++ (){val += step_;} bool operator != (range_iterator& x){return step_ > 0 ? val < x.val : val > x.val;} }; range(Integer len) : start_(0), end_(len), step_(1) {} range(Integer start, Integer end) : start_(start), end_(end), step_(1) {} range(Integer start, Integer end, Integer step) : start_(start), end_(end), step_(step) {} range_iterator begin(){ return range_iterator(start_, step_); } range_iterator   end(){ return range_iterator(  end_, step_); } };

  inline string operator "" _s (const char* str, size_t size){ return move(string(str)); }
  constexpr Integer my_pow(Integer x, Integer k, Integer z=1){return k==0 ? z : k==1 ? z*x : (k&1) ? my_pow(x*x,k>>1,z*x) : my_pow(x*x,k>>1,z);}
  constexpr Integer my_pow_mod(Integer x, Integer k, Integer M, Integer z=1){return k==0 ? z%M : k==1 ? z*x%M : (k&1) ? my_pow_mod(x*x%M,k>>1,M,z*x%M) : my_pow_mod(x*x%M,k>>1,M,z);}
  constexpr unsigned long long operator "" _ten (unsigned long long value){ return my_pow(10,value); }

  inline int k_bit(Integer x, int k){return (x>>k)&1;} //0-indexed

  mt19937 mt(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count());

  template<class T> string join(const vector<T>& v, const string& sep){ stringstream ss; for(size_t i=0; i<v.size(); i++){ if(i>0) ss << sep; ss << v[i]; } return ss.str(); }

  inline string operator * (string s, int k){ string ret; while(k){ if(k&1) ret += s; s += s; k >>= 1; } return ret; }
}
constexpr long long mod = 9_ten + 7;



int main(){
  int n,m;
  cin >> n,m;

  vector<long long> s(m);
  vector<int> u(m), v(m);

  vector<vector<int>> G(n);
  for(int i=0; i<m; i++){
    cin >> u[i],v[i],s[i];
    u[i]--; v[i]--;
    G[u[i]].push_back( i );
    G[v[i]].push_back( i );
  }

  auto check = [&](vector<long long>& val){
    queue<int> q;
    vector<int> visit(n);
    q.push(0);
    visit[0] = true;
    while(q.size()){
      int p = q.front(); q.pop();
      if( val[p] <= 0 ) return false;
      for(auto e : G[p]){
        int nx = u[e]^v[e]^p;
        if( s[e] != val[p] + val[nx] ) return false;
        if( visit[nx] == false ){
          visit[nx] = true;
          q.push(nx);
        }
      }
    }
    return true;
  };

  auto paint = [&](vector<long long>& val, int start, long long sc){
    queue<int> q;
    vector<int> visit(n);
    q.push(start);
    visit[start] = true;
    val[start] = sc;
    while(q.size()){
      int p = q.front(); q.pop();
      for(auto e : G[p]){
        int nx = u[e]^v[e]^p;
        if( visit[nx] == false ){
          visit[nx] = true;
          val[nx] = s[e] - val[p];
          q.push(nx);
        }
      }
    }
    return true;
  };

  vector<long long> w(n, 0);
  vector<int> dist(n, -1);
  int odd = -1;
  long long c = -1;
  function<void(int)> dfs = [&](int p){
    int d = dist[p];
    for(auto e : G[p]){
      int nx = p^u[e]^v[e];
      if( dist[nx] != -1 ){
        if( abs(d+1-dist[nx]) > 1 && abs(d+1-dist[nx])%2 ){
          odd = nx;
          long long w_ = s[e]-w[p];
          c = (w_ + w[nx]) / 2;
        }
      }else{
        dist[nx] = d+1;
        w[nx] = s[e]-w[p];
        dfs(nx);
      }
    }
  };
  dist[0] = 0;
  dfs(0);

  vector<long long> val(n);
  if( odd != -1 ){
    paint(val, odd, c);
    if(check(val)){
      println(1);
    }else{
      println(0);
    }
  }else{
    long long lmin = 1ll<<50, rmin = 1ll<<50;
    for(int i=0; i<n; i++){
      if(dist[i]%2==0) lmin = min(lmin, w[i]);
      else rmin = min(rmin, w[i]);
    }

    long long xmin = 1-lmin;
    long long xmax = rmin-1;

    paint(val, 0, xmin);
    if( check(val) == false ){
      println(0);
    }else{
      eprintln( xmax, xmin );
      println( max(0ll, xmax-xmin+1) );
    }


  }


  return 0;
}


Measured memory_bytes: 17408