#pragma GCC optimize("Ofast")
#include<bits/stdc++.h>
// #include<ext/pb_ds/assoc_container.hpp>
// #include<ext/pb_ds/tree_policy.hpp>
// #include<ext/pb_ds/tag_and_trait.hpp>
// using namespace __gnu_pbds;
// #include<boost/multiprecision/cpp_int.hpp>
// namespace multiprecisioninteger = boost::multiprecision;
// using cint=multiprecisioninteger::cpp_int;
using namespace std;
using ll=long long;
#define double long double
using datas=pair<ll,ll>;
using ddatas=pair<double,double>;
using tdata=pair<ll,datas>;
using vec=vector<ll>;
using mat=vector<vec>;
using pvec=vector<datas>;
using pmat=vector<pvec>;
// using llset=tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>;
#define For(i,a,b) for(i=a;i<(ll)b;++i)
#define bFor(i,b,a) for(i=b,--i;i>=(ll)a;--i)
#define rep(i,N) For(i,0,N)
#define rep1(i,N) For(i,1,N)
#define brep(i,N) bFor(i,N,0)
#define brep1(i,N) bFor(i,N,1)
#define all(v) (v).begin(),(v).end()
#define allr(v) (v).rbegin(),(v).rend()
#define vsort(v) sort(all(v))
#define vrsort(v) sort(allr(v))
#define endl "\n"
#define eb emplace_back
#define print(v) cout<<v<<endl
#define printyes cout<<"Yes"<<endl
#define printno cout<<"No"<<endl
#define printYES cout<<"YES"<<endl
#define printNO cout<<"NO"<<endl
#define output(v) do{bool f=0;for(auto outi:v){cout<<(f?" ":"")<<outi;f=1;}cout<<endl;}while(0)
#define matoutput(v) do{for(auto outimat:v)output(outimat);}while(0)
const ll mod=1000000007;
// const ll mod=998244353;
const ll inf=1LL<<60;
const double PI = acos(-1);
const double eps = 1e-9;
template<class T> inline bool chmax(T& a,T b){bool x=a<b;if(x)a=b;return x;} 
template<class T> inline bool chmin(T& a,T b){bool x=a>b;if(x)a=b;return x;} 

void startupcpp(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout<<fixed<<setprecision(15);
}

ll gcd(ll a,ll b){if(!b)return abs(a);return (a%b==0)?abs(b):gcd(b,a%b);}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

int main(){
  startupcpp();
  ll i,j,N,M,c;
  cin>>N>>M;
  pmat g(N);
  pvec dist(N,datas(0,0));
  while(M--){
    cin>>i>>j>>c;
    --i;--j;
    g[i].eb(c,j);
    g[j].eb(c,i);
  }
  c=0;
  queue<tdata> que;
  que.push(tdata(0,datas(1,0)));
  while(!que.empty()){
    tdata x=que.front();que.pop();
    if(dist[x.first]!=datas(0,0)){
      if(dist[x.first]==x.second)continue;
      if(dist[x.first].first<x.second.first)swap(dist[x.first],x.second);
      c=x.second.second-dist[x.first].second;
      if(dist[x.first].first==x.second.first||c<=0||c&1){
        print(0);
        return 0;
      }
      c>>=1;
      break;
    }
    dist[x.first]=x.second;
    for(datas next:g[x.first]){
      que.push(tdata(next.second,datas(-x.second.first,next.first-x.second.second)));
    }
  }
  if(c){
    queue<datas> sque;
    vec sdist(N,inf);
    sque.push(datas(c,0));
    while(!sque.empty()){
      datas x=sque.front();sque.pop();
      if(sdist[x.second]!=inf||x.first<=0){
        if(sdist[x.second]==x.first)continue;
        print(0);
        return 0;
      }
      sdist[x.second]=x.first;
      for(datas next:g[x.second]){
        next.first-=x.first;
        sque.push(next);
      }
    }
    print(1);
  }else{
    ll mi=1,ma=inf;
    rep(i,N){
      if(dist[i].first==1){
        chmax(mi,-dist[i].second+1);
      }else{
        chmin(ma,dist[i].second-1);
      }
    }
    print(max(0LL,ma-mi+1));
  }
}

Measured memory_bytes: 11904