#include <bits/stdc++.h>
#include <unistd.h>
 
using namespace std;
 
typedef long long ll;
typedef pair<ll,ll> P;
 
long long int INF = 3e18;
const ll fact_table = 5000000;
double Pi = 3.1415926535897932384626;
 
//vector<ll> G[550010];
vector<P> tree[500010];
priority_queue <ll> pql;
priority_queue <P> pqp;
//big priority queue
priority_queue <ll,vector<ll>,greater<ll> > pqls;
priority_queue <P,vector<P>,greater<P> > pqps;
//small priority queue
//top pop
 
int dx[8]={1,0,-1,0,1,1,-1,-1};
int dy[8]={0,1,0,-1,1,-1,-1,1};
char dir[] = "DRUL";
//ll bit[500005];
//↓,→,↑,←
 
 
#define p(x) cout<<x<<"\n";
#define el cout<<endl;
#define pe(x) cout<<(x)<<" ";
#define ps(x) cout<<fixed<<setprecision(25)<<x<<endl;
#define pu(x) cout<<(x);
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define CLEAR(a) a = decltype(a)(); 
 

ll mod = 998244353;
//ll mod = 1000000007;
 
ll rui(ll number1,ll number2){
 
    if(number2 == 0){
        return 1;
    }else{
        ll number3 = rui(number1,number2 / 2);
        number3 *= number3;
        number3 %= mod;
        if(number2%2==1){
            number3 *= number1;
            number3 %= mod;
        }
        return number3;
    }
}
ll gcd(ll number1,ll number2){
 
    if(number1 > number2){
        swap(number1,number2);
    }
    if(number1 == 0 || number1 == number2){
        return number2;
    }else{
        return gcd(number2 % number1,number1);
    }
}
void YES(bool condition){
 
    if(condition){
        p("YES");
    }else{
        p("NO");
    }
    return;
}
void Yes(bool condition){

    if(condition){
        p("Yes");
    }else{
        p("No");
    }
    return;
}
 

ll fact[fact_table + 5],rfact[fact_table + 5];
 
void c3_init(){
    fact[0] = rfact[0] = 1;
    for(ll i=1; i<=fact_table; i++){
        fact[i] = (fact[i-1]*i) % mod;
    }
    rfact[fact_table] = rui(fact[fact_table],mod - 2);
    for(ll i=fact_table; i>=1; i--){
       rfact[i-1] = rfact[i] * i;
       rfact[i-1] %= mod;
    }
    return;}
ll c3(ll n,ll r){
    return (((fact[n] * rfact[r]) % mod ) * rfact[n-r]) % mod;}

 
ll n,m,num,sum,a,b,c,d,e,g,h,w,i,j,q,r,l;
ll k,idx,ans;
ll x[500005],y[500005],z[500005];
bool used[500005], pos[500005];
ll offset[500005];
char s[500005];

void dfs(ll v,ll p,bool c_pos,ll c_offset){
    used[v] = true;
    pos[v] = true;
    offset[v] = c_offset;
    pos[v] = c_pos;
    for(int i=0;i<tree[v].size();i++){
        ll nv = tree[v][i].first;
        ll bring_offset = tree[v][i].second - c_offset;
        bool bring_pos = !c_pos;
        if(nv == p || used[nv])continue;
        dfs(nv, v, bring_pos, bring_offset);
    }
}
int main(){
    cin >> n >> m;
    for(int i=0;i<m;i++){
        cin >> a >> b >> c;
        x[i] = a;
        y[i] = b;
        z[i] = c;
        tree[a].pb(P(b,c));
        tree[b].pb(P(a,c));
    }
    dfs(1, -1, true, 0);
    for(int i=1;i<=n;i++){
       // pe(i);pe(offset[i]);p(pos[i]);
    }
    ll min_x = 1;
    ll max_x = INF;
    bool ng = false;
    bool onlyone = false;
    ll chance_x = -1;
    for(int i=0;i<m;i++){
        ll v1 = x[i], v2 = y[i];
        if(pos[v1] != pos[v2]){
            //正負が一致していない
            if(offset[v1] + offset[v2] == z[i]){
                if(pos[v1]){
                    min_x = max(min_x, 1 - offset[v1]);
                    max_x = min(max_x, - 1 + offset[v2]);
                }else{
                    min_x = max(min_x, 1 - offset[v2]);
                    max_x = min(max_x, - 1 + offset[v1]);
                }
                if(min_x > max_x){
                    ng = true;
                    break;
                }
                continue;
            }else{
                ng = true;
                break;
            }
        }else{
            if(!onlyone){
                onlyone = true;
                ll twox = z[i] - offset[v1] - offset[v2];
                if(!pos[v1]){
                    twox *= -1;
                }
                if(twox % 2 == 1){
                    ng = true;
                    break;
                }else{
                    chance_x = twox / 2;
                }
            }else{
                ll twox;
                if(pos[v1]){
                    twox = z[i] - offset[v1] - offset[v2];
                }else{
                    twox = offset[v1] + offset[v2] - z[i];
                }
                if(twox == chance_x * 2){
                    continue;
                }else{
                    ng = true;
                    break;
                }
            }
        }
    }
    if(ng){
        p(0);
    }else if(onlyone){
        if(min_x <= chance_x && chance_x <= max_x){
            p(1);
        }else{
            p(0);
        }
    }else{
        if(max_x < min_x){
            ans = 0;
        }else{
            ans = max_x - min_x + 1;
        }
        p(ans);
    }
    
    return 0;
    
    
}











Measured memory_bytes: 37120