#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define sar(a,n) cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl
#define svec(v) cout<<#v<<":";rep(pachico,v.size())cout<<" "<<v[pachico];cout<<endl
#define svecp(v) cout<<#v<<":";each(pachico,v)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl
#define sset(s) cout<<#s<<":";each(pachico,s)cout<<" "<<pachico;cout<<endl
#define smap(m) cout<<#m<<":";each(pachico,m)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 100005;

struct edge
{
    ll to,cost;
};

vector<edge> G[MAX_N];
//(1or-1,c)
ll fix,mn,mx;
pll val[MAX_N];
ll visit[MAX_N];

bool dfs(int u)
{
    visit[u] = 1;
    each(e,G[u]){
        if(visit[e.to] == 0){
            if(val[u].fi == 1){
                if(e.cost-val[u].se < mn+1) return false;
                mx = min(mx,e.cost-val[u].se-1);
                val[e.to] = pll(-1,e.cost-val[u].se);
            }else{
                if(mx+e.cost-val[u].se < 1) return false;
                mn = max(mn,val[u].se+1-e.cost);
                val[e.to] = pll(1,e.cost-val[u].se);
            }
            if(!dfs(e.to)){
                return false;
            }
        }else if(visit[e.to] == 1){
            if(val[u].fi != val[e.to].fi){
                if(val[u].se + val[e.to].se != e.cost) return false;
            }else{
                ll cri = abs(e.cost-val[u].se-val[e.to].se);
                if(cri > 0 && cri % 2 == 0){
                    fix = cri/2;
                }
                return false;
            }
        }
    }
    visit[u] = 2;
    return true;
}

bool check(int u)
{
    each(e,G[u]){
        if(visit[e.to] == 0){
            if(e.cost-visit[u] <= 0) return false;
            visit[e.to] = e.cost-visit[u];
            if(!check(e.to)){
                return false;
            }
        }else if(visit[e.to] > 0){
            if(visit[u]+visit[e.to] != e.cost) return false;
        }
    }
    return true;
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,m;
    cin >> n >> m;
    rep(i,m){
        ll u,v,c;
        cin >> u >> v >> c;
        G[u-1].pb((edge){v-1,c});
        G[v-1].pb((edge){u-1,c});
    }
    val[0] = pll(1,0);
    mn = 1, mx = INF;
    fix = -1;
    bool res = dfs(0);
    if(fix > 0){
        rep(i,n){
            visit[i] = 0;
        }
        visit[0] = fix;
        cout << check(0) << "\n";
    }else{
        if(res){
            cout << max(0LL,mx-mn+1) << "\n";
        }else{
            cout << "0\n";
        }
    }
    return 0;
}


Measured memory_bytes: 14848