#include <bits/stdc++.h>

#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 reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))
#define sz(v) ((int) v.size())

using namespace std;

using i64 = long long;
using f80 = long double;
using vi32 = vector<int>;
using vi64 = vector<i64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

void yes() { cout << "Yes" << endl; exit(0); }
void no() { cout << "No" << endl; exit(0); }
template <typename T> class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T> class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> void amax(T &x, T y) { x = max(x, y); }
template <typename T> void amin(T &x, T y) { x = min(x, y); }
template <typename T> T exp(T x, i64 n, T e = 1) { T r = e; while (n > 0) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; }
template <typename T> istream& operator>>(istream &is, vector<T> &v) { for (auto &x : v) is >> x; return is; }
template <typename T> ostream& operator<<(ostream &os, vector<T> &v) { rep(i, v.size()) { if (i) os << ' '; os << v[i]; } return os; }
void solve(); int main() { ios::sync_with_stdio(0); cin.tie(0); cout << fixed << setprecision(16); solve(); return 0; }

template <typename T, typename U>
vector<U> make_vector(T&& n, U&& val) {
  return vector<U>(forward<T>(n), forward<U>(val));
}
template <typename T, typename... Args>
decltype(auto) make_vector(T&& n, Args&&... args) {
  return vector<decltype(make_vector(forward<Args>(args)...))>(forward<T>(n), make_vector(forward<Args>(args)...));
}

const int INF = 1001001001;
const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};

void solve() {
  int n, m;
  cin >> n >> m;
  using P = pair<int, int>;
  vector<vector<P>> g(n);
  map<P, int> mp;
  rep(i, m) {
    int u, v, s;
    cin >> u >> v >> s;
    u--, v--;
    g[u].emplace_back(v, s);
    g[v].emplace_back(u, s);
    mp[P(u, v)] = s;
  }
  bool bipartite_graph;
  int base;
  {
    // 二部グラフ判定
    vi32 dist(n, INF);
    auto dfs = [&](auto dfs, int u, int d) -> bool {
      if (dist[u] != INF) {
        if (dist[u] % 2 != d % 2) {
          base = u;
          return false;
        }
        return true;
      }
      dist[u] = d;
      for (auto p : g[u]) {
        int v, s;
        tie(v, s) = p;
        if (!dfs(dfs, v, d + 1)) {
          return false;
        }
      }
      return true;
    };
    bipartite_graph = dfs(dfs, 0, 0);
  }
  vi64 value(n, -1e18);
  vi32 evenodd(n);
  auto dfs = [&](auto dfs, int u, i64 val, int eo) -> bool {
    if (value[u] != -1e18) {
      return value[u] == val;
    }
    value[u] = val;
    evenodd[u] = eo;
    for (auto e : g[u]) {
      int v, s;
      tie(v, s) = e;
      i64 nval = (i64) s - val;
      if (!dfs(dfs, v, nval, 1 - eo)) {
        return false;
      }
    }
    return true;
  };
  if (bipartite_graph) {
    if (!dfs(dfs, 0, 1, 0)) {
      cout << 0 << endl;
      return;
    }
    i64 mi = 1e18;
    int mi_i = -1;
    i64 odd_mi = 1e18;
    rep(i, n) {
      if (mi >= value[i]) {
        mi = value[i];
        mi_i = i;
        if (mi <= 0 && evenodd[i]) {
          cout << 0 << endl;
          return;
        }
      }
      if (evenodd[i] && odd_mi >= value[i]) {
        odd_mi = value[i];
      }
    }
    if (mi <= 0) {
      value.assign(n, -1e18);
      dfs(dfs, mi_i, 1, 0);
      mi = 1e18;
      odd_mi = 1e18;
      rep(i, n) {
        if (mi >= value[i]) {
          mi = value[i];
          if (mi <= 0) {
            cout << 0 << endl;
            return;
          }
        }
        if (evenodd[i] && odd_mi >= value[i]) {
          odd_mi = value[i];
        }
      }
    }
    cout << odd_mi << endl;
    return;
  }
  vi32 path;
  {
    vi32 dist(n, INF);
    auto dfs2 = [&](auto dfs2, int u, int d) -> bool {
      if (dist[u] != INF) {
        if (u == base && dist[u] % 2 != d % 2) {
          return true;
        }
        return false;
      }
      dist[u] = d;
      for (auto e : g[u]) {
        int v, s;
        tie(v, s) = e;
        if (dfs2(dfs2, v, d + 1)) {
          path.push_back(v);
          return true;
        }
      }
      return false;
    };
    dfs2(dfs2, base, 0);
    path.push_back(base);
    i64 sum = 0;
    rep(i, sz(path)) {
      int j = (i + 1) % sz(path);
      int u = path[i], v = path[j];
      if (u > v) swap(u, v);
      sum += mp[P(u, v)] * (i % 2 == 0 ? 1 : -1);
    }
    if (sum % 2 == 1) {
      cout << 0 << endl;
      return;
    }
    i64 val = sum / 2;
    if (!dfs(dfs, base, val, 0)) {
      cout << 0 << endl;
    } else {
      i64 mi = *min_element(all(value));
      if (mi <= 0) {
        cout << 0 << endl;
      } else {
        cout << 1 << endl;
      }
    }
  }
}


Measured memory_bytes: 24552