#include <bits/stdc++.h>
#include <sys/time.h>
using namespace std;

#define rep(i,n) for(long long i = 0; i < (long long)(n); i++)
#define repi(i,a,b) for(long long i = (long long)(a); i < (long long)(b); i++)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define mt make_tuple
#define mp make_pair
template<class T1, class T2> bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); }
template<class T1, class T2> bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

using ll = long long; using vll = vector<ll>; using vvll = vector<vll>; using P = pair<ll, ll>;
using ld = long double;  using vld = vector<ld>; 
using vi = vector<int>; using vvi = vector<vi>; vll conv(vi& v) { vll r(v.size()); rep(i, v.size()) r[i] = v[i]; return r; }

inline void input(int &v){ v=0;char c=0;int p=1; while(c<'0' || c>'9'){if(c=='-')p=-1;c=getchar();} while(c>='0' && c<='9'){v=(v<<3)+(v<<1)+c-'0';c=getchar();} v*=p; } // これを使うならば、tieとかを消して！！
template <typename T, typename U> ostream &operator<<(ostream &o, const pair<T, U> &v) {  o << "(" << v.first << ", " << v.second << ")"; return o; }
template<size_t...> struct seq{}; template<size_t N, size_t... Is> struct gen_seq : gen_seq<N-1, N-1, Is...>{}; template<size_t... Is> struct gen_seq<0, Is...> : seq<Is...>{};
template<class Ch, class Tr, class Tuple, size_t... Is>
void print_tuple(basic_ostream<Ch,Tr>& os, Tuple const& t, seq<Is...>){ using s = int[]; (void)s{0, (void(os << (Is == 0? "" : ", ") << get<Is>(t)), 0)...}; }
template<class Ch, class Tr, class... Args> 
auto operator<<(basic_ostream<Ch, Tr>& os, tuple<Args...> const& t) -> basic_ostream<Ch, Tr>& { os << "("; print_tuple(os, t, gen_seq<sizeof...(Args)>()); return os << ")"; }
ostream &operator<<(ostream &o, const vvll &v) { rep(i, v.size()) { rep(j, v[i].size()) o << v[i][j] << " "; o << endl; } return o; }
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T> ostream &operator<<(ostream &o, const deque<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const unordered_set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U>  ostream &operator<<(ostream &o, const map<T, U> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U, typename V>  ostream &operator<<(ostream &o, const unordered_map<T, U, V> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it; o << "]";  return o; }
vector<int> range(const int x, const int y) { vector<int> v(y - x + 1); iota(v.begin(), v.end(), x); return v; }
template <typename T> istream& operator>>(istream& i, vector<T>& o) { rep(j, o.size()) i >> o[j]; return i;}
template <typename T, typename S, typename U> ostream &operator<<(ostream &o, const priority_queue<T, S, U> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.top(); tmp.pop(); o << x << " ";} return o; }
template <typename T> ostream &operator<<(ostream &o, const queue<T> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.front(); tmp.pop(); o << x << " ";} return o; }
template <typename T> ostream &operator<<(ostream &o, const stack<T> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.top(); tmp.pop(); o << x << " ";} return o; }
template <typename T> unordered_map<T, ll> counter(vector<T> vec){unordered_map<T, ll> ret; for (auto&& x : vec) ret[x]++; return ret;};
string substr(string s, P x) {return s.substr(x.fi, x.se - x.fi); }
void vizGraph(vvll& g, int mode = 0, string filename = "out.png") { ofstream ofs("./out.dot"); ofs << "digraph graph_name {" << endl; set<P> memo; rep(i, g.size())  rep(j, g[i].size()) { if (mode && (memo.count(P(i, g[i][j])) || memo.count(P(g[i][j], i)))) continue; memo.insert(P(i, g[i][j])); ofs << "    " << i << " -> " << g[i][j] << (mode ? " [arrowhead = none]" : "")<< endl;  } ofs << "}" << endl; ofs.close(); system(((string)"dot -T png out.dot >" + filename).c_str()); }
size_t random_seed; namespace std { using argument_type = P; template<> struct hash<argument_type> { size_t operator()(argument_type const& x) const { size_t seed = random_seed; seed ^= hash<ll>{}(x.fi); seed ^= (hash<ll>{}(x.se) << 1); return seed; } }; }; // hash for various class
struct timeval start; double sec() { struct timeval tv; gettimeofday(&tv, NULL); return (tv.tv_sec - start.tv_sec) + (tv.tv_usec - start.tv_usec) * 1e-6; }
struct init_{init_(){ ios::sync_with_stdio(false); cin.tie(0); gettimeofday(&start, NULL); struct timeval myTime; struct tm *time_st; gettimeofday(&myTime, NULL); time_st = localtime(&myTime.tv_sec); srand(myTime.tv_usec); random_seed = RAND_MAX / 2 + rand() / 2; }} init__;
#define ldout fixed << setprecision(40) 

#define EPS (double)1e-14
#define INF (ll)1e18
#define mo  (ll)(1e9+7)

ll n, m;
vector<vector<P>> g;
vector<P> memo;

void dfs(ll v, ll p) {
    P t = memo[v];
    for (auto us : g[v]) {
//        cout << v << " " << us <<endl;
        ll u = us.fi;
        ll s = us.se;
        if (u == p) continue;
        if (memo[u].fi != INF) continue;

        memo[u].fi = -t.fi;
        memo[u].se = s-t.se;
        dfs(u, v);
    }
}

vll y;
void df(ll v, ll p) {
    for (auto u : g[v]) if (u.fi != p) {
        if (y[u.fi] != INF) continue;
        y[u.fi] = u.se - y[v];
        df(u.fi, v);
    }
}

ll brutal(void) {
    y.resize(n);
    ll M = 0;
    rep(i, m) {
        for (auto us : g[i]) {
            chmax(M, us.se);
        }
    }
    ll ret = 0;
    rep(val, M) {
        rep(i, n) y[i] = INF;
        y[0] = val;
        df(0, -1);
//        cout << y << endl;
        ll faf = 1;
        rep(i, n) {
            faf &= y[i] > 0;
        }
        rep(v, n) {
            for (auto us: g[v]) {
                faf &= y[v] + y[us.fi] == us.se;
            }
        }
        ret += faf;
    }
    return ret;
}

ll solve(void) {
    memo[0] = P(1, 0);
    dfs(0, -1); // a + 0
////    cout << memo << endl;

    ll a = INF; // not yet decided
    rep(v, n) {
        for (auto e : g[v]) {
            ll u = e.fi;
            ll s = e.se;
            P tmp;
            tmp.fi = memo[v].fi + memo[u].fi;
            tmp.se = memo[v].se + memo[u].se - s;
            if (tmp.fi == 0) {
                if (tmp.se != 0) {
                    return 0;
                }
            } else {
                if (tmp.fi < 0) tmp.fi *= -1, tmp.se *= -1;
                // a fi + se = 0;
                // a = -se/fi
                if (tmp.se % tmp.fi != 0) {
                    return 0;
                }
                if (a == INF) {
                    a = -tmp.se/tmp.fi;
                } else {
                    if (a != -tmp.se/tmp.fi) {
                        return 0;
                    }
                }
            }
        }
    }
    if (a != INF) {
        if (a > 0) {
            y.resize(n);
            rep(i, n) y[i] = INF;
            y[0] = a;
            df(0, -1);
            ll faf = 1;
            rep(i, n) {
                faf &= y[i] > 0;
            }
            rep(v, n) {
                for (auto us: g[v]) {
                    faf &= y[v] + y[us.fi] == us.se;
                }
            }
            if (faf) 
                return 1;
            else 
                return 0;

        } else {
            return 0;
        }
    } else {
        ll l = 1, r = INF;
        rep(i, n) {
            if (memo[i].fi == -1) {
                chmin(r,memo[i].se-1);
            } else {
                chmax(l, 1-memo[i].se);
            }
        }
        return max<ll>(0ll, r - l + 1ll);
    }
}

int main(void) {
    cin >> n >> m;
    memo.resize(n);
    rep(i, n) {
        memo[i] = P(INF, INF);
    }
    g.resize(n);
    rep(i, m) {
        ll u, v, s; cin >> u >> v >> s; u--, v--;
        g[u].pb(P(v,s));
        g[v].pb(P(u,s));
    }

       cout << solve() << endl;
    /*
       brutal();
       return 0;
       */

    /*
    if (brutal() != solve()) {
        cout <<"HIT" << brutal() << " " << solve() <<endl;
        cout << n << " " << m << endl;
        cout << g << endl;

    }
    */
    return 0;
}


Measured memory_bytes: 17276