#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 <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;

vector<long long> u,v,s;
bool ok = true;

vector<long long> w;

pair<long long, int> dfs(vector<vector< pair<int,int> >>& G, int pos, int e){
  w[pos] = s[e] - w[ u[e]^v[e]^pos ];
  if( w[pos] <= 0 ){
    ok = false;
    return {1, pos};
  }

  for(int i=0; i<G[pos].size(); i++){
    int nx = G[pos][i].first;
    int ee = G[pos][i].second;
    long long s_ = s[ee] - w[pos];

    if( w[nx] != 1145148931919ll ){
      if( w[nx] != s_ ){
        ok = false;
        return {(w[nx]+s_)/2, nx};
      }
    }else{
      auto res = dfs(G, nx, ee);
      if( !ok ) return res;
    }
  }

  return {w[pos], pos};
}

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

  u.resize(m); v.resize(m);
  s.resize(m);

  vector<vector< pair<int,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( {v[i], i} );
    G[v[i]].push_back( {u[i], i} );
  }

  w = vector<long long>(n, 1145148931919ll);

  int start = 0;
  w[start] = 1;

  for(int t=0; t<32; t++){
    ok = true;

    bool okok = true;
    for(int i=0; i<G[start].size(); i++){
      auto tmp = dfs(G, G[start][i].first, G[start][i].second);
      // if( !ok ){
      //   println(0);
      //   return 0;
      // }

      if( !ok ){
        w =  vector<long long>(n, 1145148931919ll);
        start = tmp.second;
        w[ start ] = tmp.first;
        okok = false;
        break;
      }
    }

    if(okok) break;

    if(t==31 && !okok){
      println(0);
      return 0;
    }
  }

  long long lo,hi;

  auto check = [&](long long w0){
    w = vector<long long>(n, 1145148931919ll);
    w[0] = w0;
    ok = true;
    bool okok = true;
    for(int i=0; i<G[0].size(); i++){
      auto tmp = dfs(G, G[0][i].first, G[0][i].second);
      if( !ok || tmp.first <= 0 ){
        okok = false;
        break;
      }
    }
    return okok;
  };


  long long w0_base = w[0];

  assert( check(w0_base) );


  {
    long long lb = 0;
    long long ub = w0_base;
    while(ub-lb>1){
      long long mid = (lb+ub)/2;
      bool ok = check(mid);
      (ok? ub : lb) = mid;
    }
    lo = ub;
  }

  {
    long long lb = w0_base;
    long long ub = 1000000001;
    while(ub-lb>1){
      long long mid = (lb+ub)/2;
      bool ok = check(mid);
      (ok? lb : ub) = mid;
    }
    hi = lb;
  }

  println(hi-lo+1);

  // for(int i=lo; i<=hi; i++){
  //   assert( check(i) );
  //   eprintln(w);
  // }
  return 0;
}


Measured memory_bytes: 15840