#include <bits/stdc++.h>
                                            #include<iostream>
                                            #include<cstdio>
                                            #include<vector>
                                            #include<queue>
                                            #include<map>
                                            #include<cstring>
                                            #include<string>
                                            #include <math.h>
                                            #include<algorithm>
                                        //    #include <boost/multiprecision/cpp_int.hpp>
                                            #include<functional>
                                   #define int long long
                                            #define inf  1000000007
                                            #define pa pair<int,int>
                                            #define ll long long
                                            #define pal pair<double,double>
                                            #define ppap pair<pa,int>
                                      #define PI 3.14159265358979323846
                                            #define paa pair<int,char>
                                            #define  mp make_pair
                                            #define  pb push_back
                                            #define EPS (1e-10)
                                            #define equals(a,b) (fabs((a)-(b))<EPS)
    int dx[4]={0,-1,0,1};
    int dy[4]={1,0,-1,0};
                                            using namespace std;
                                   			class pa3{
                                            	public:
                                            	int x,y,z;
                                            	pa3(int x=0,int y=0,int z=0):x(x),y(y),z(z) {}
                                            	bool operator < (const pa3 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		 return z<p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                   				bool operator > (const pa3 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		 return z>p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa3 &p) const{
                                            		return x==p.x && y==p.y && z==p.z;
                                            	}
                                            		bool operator != (const pa3 &p) const{
                                            			return !( x==p.x && y==p.y && z==p.z);
                                            	}
                                            
                                            };
                                            
                                            class pa4{
                                            	public:
                                            	double x;
                                            	int y,z,w;
                                            	pa4(double x=0,int y=0,int z=0,int w=0):x(x),y(y),z(z),w(w) {}
                                            	bool operator < (const pa4 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		if(z!=p.z)return z<p.z;
                                            		return w<p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator > (const pa4 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		if(z!=p.z)return z>p.z;
                                            		return w>p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa4 &p) const{
                                            		return x==p.x && y==p.y && z==p.z &&w==p.w;
                                            	}
                                            		
                                            
                                            };
                                            class pa2{
                                            	public:
                                            	int x,y;
                                            	pa2(int x=0,int y=0):x(x),y(y) {}
                                            	pa2 operator + (pa2 p) {return pa2(x+p.x,y+p.y);}
                                            	pa2 operator - (pa2 p) {return pa2(x-p.x,y-p.y);}
                                            	bool operator < (const pa2 &p) const{
                                            		return y != p.y ? y<p.y: x<p.x;
                                            	}
                                            	bool operator > (const pa2 &p) const{
                                            		return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa2 &p) const{
                                            		return abs(x-p.x)==0 && abs(y-p.y)==0;
                                            	}
                                            	bool operator != (const pa2 &p) const{
                                            		return !(abs(x-p.x)==0 && abs(y-p.y)==0);
                                            	}
                                            		
                                            
                                            };
                                            
                                                   #define ppa pair<int,pas>
                                            class Point{
                                            	public:
                                            	double x,y;
                                            	Point(double x=0,double y=0):x(x),y(y) {}
                                            	Point operator + (Point p) {return Point(x+p.x,y+p.y);}
                                            	Point operator - (Point p) {return Point(x-p.x,y-p.y);}
                                            	Point operator * (double a) {return Point(x*a,y*a);}
                                            	Point operator / (double a) {return Point(x/a,y/a);}
                                            	double absv() {return sqrt(norm());}
                                            	double norm() {return x*x+y*y;}
                                            	bool operator < (const Point &p) const{
                                            		return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const Point &p) const{
                                            		return fabs(x-p.x)<EPS && fabs(y-p.y)<EPS;
                                            	}
                                            };
                                            typedef Point Vector;
                                     #define pl pair<int,pas>
                                            struct Segment{
                                            Point p1,p2;
                                            };
                                             double dot(Vector a,Vector b){
                                            	return a.x*b.x+a.y*b.y;
                                            }
                                            double cross(Vector a,Vector b){
                                            	return a.x*b.y-a.y*b.x;
                                            }
                                        
                bool parareru(Point a,Point b,Point c,Point d){
                //	if(abs(cross(a-b,d-c))<EPS)cout<<"dd "<<cross(a-b,d-c)<<endl;
                	return abs(cross(a-b,d-c))<EPS;
                }
                double distance_ls_p(Point a, Point b, Point c) {
                  if ( dot(b-a, c-a) < EPS ) return (c-a).absv();
                  if ( dot(a-b, c-b) < EPS ) return (c-b).absv();
                  return abs(cross(b-a, c-a)) / (b-a).absv();
                }
                bool is_intersected_ls(Segment a,Segment b) {
                	if(a.p1==b.p1||a.p2==b.p1||a.p1==b.p2||a.p2==b.p2) return false;
                	if(parareru((a.p2),(a.p1),(a.p1),(b.p2))&&parareru((a.p2),(a.p1),(a.p1),(b.p1))){
                //		cout<<"sss"<<endl;
                		if(dot(a.p1-b.p1,a.p1-b.p2)<EPS) return true;
                		if(dot(a.p2-b.p1,a.p2-b.p2)<EPS) return true;
                		if(dot(a.p1-b.p1,a.p2-b.p1)<EPS) return true;
                		if(dot(a.p1-b.p2,a.p2-b.p2)<EPS) return true;
                		return false;
                	}
                  else return ( cross(a.p2-a.p1, b.p1-a.p1) * cross(a.p2-a.p1, b.p2-a.p1) < EPS ) && ( cross(b.p2-b.p1, a.p1-b.p1) * cross(b.p2-b.p1, a.p2-b.p1) < EPS );
                }
                 
                double segment_dis(Segment a,Segment b){
                	if(is_intersected_ls(a,b))return 0;
                	double r=distance_ls_p(a.p1, a.p2, b.p1);
                	r=min(r,distance_ls_p(a.p1, a.p2, b.p2));
                	r=min(r,distance_ls_p(b.p1, b.p2, a.p2));
                	r=min(r,distance_ls_p(b.p1, b.p2, a.p1));
                	return r;
                }
                Point intersection_ls(Segment a, Segment b) {
                  Point ba = b.p2-b.p1;
                  double d1 = abs(cross(ba, a.p1-b.p1));
                  double d2 = abs(cross(ba, a.p2-b.p1));
                  double t = d1 / (d1 + d2);
                 
                  return a.p1 + (a.p2-a.p1) * t;
                }
                 
                                string itos( int i ) {
                                ostringstream s ;
                                s << i ;
                                return s.str() ;
                                }
                                 
                                int gcd(int v,int b){
                                	if(v>b) return gcd(b,v);
                                	if(v==b) return b;
                                	if(b%v==0) return v;
                                	return gcd(v,b%v);
                                }
                 
                                double distans(double x1,double y1,double x2,double y2){
                                	double rr=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
                                	return sqrt(rr);
                                	
                                }
                                int mod;
                int pr[2010];
                int inv[2010];
               
                int beki(int wa,int rr,int warukazu){
                	if(rr==0) return 1%warukazu;
                	if(rr==1) return wa%warukazu;
                	if(rr%2==1) return (beki(wa,rr-1,warukazu)*wa)%warukazu;
                	int zx=beki(wa,rr/2,warukazu);
                	return (zx*zx)%warukazu;
                }
                /*
    double bekid(double w,int r){
    	if(r==0) return 1.0;
    	if(r==1) return w;
    	if(r%2) return bekid(w,r-1)*w;
    	double f=bekid(w,r/2);
    	return f*f;
    }*/
        /*        
    			int comb(int nn,int rr){
    				int r=pr[nn]*inv[rr];
    				r%=mod;
    				r*=inv[nn-rr];
    				r%=mod;
    				return r;
    			}
          */      
                void gya(int ert){
                	pr[0]=1;
                	for(int i=1;i<ert;i++){
                		pr[i]=(pr[i-1]*i)%mod;
                	}
                	for(int i=0;i<ert;i++) inv[i]=beki(pr[i],mod-2,mod);
                	
                }
                
              //   cin.tie(0);
    		//	ios::sync_with_stdio(false);
    			//priority_queue<pa3,vector<pa3>,greater<pa3>> pq;            
                 //sort(ve.begin(),ve.end(),greater<int>());
                                         //----------------kokomade tenpure------------
            
    
                //vector<double> ans(100000000),ans2(100000000)
int n,m;
vector<pa> G[100020];
int hai[100020];
bool vis[100020]={0};
int atai[100020];

void dfs_bi(int r,int val,int p){
	if(hai[r]!=-1) return;
	hai[r]=val;
	for(auto v:G[r])if(v.first!=p)dfs_bi(v.first,1-val,r);
}

void dfs_vis(int r,int val,int p){
	if(vis[r])return;
	vis[r]=1;
	atai[r]=val;
	for(auto v:G[r])if(v.first!=p)dfs_vis(v.first,v.second-val,r);
}
int ma=inf*1000000000ll;
map<pa,int> maa;
int oya[100020]={0};
vector<int> ve;
bool bo=true;
int bi[100020]={0};
void dfs(int r,int val,int p){
	if(vis[r]){
		if(bi[r]==val)return;
	//	cout<<" "<<r<<endl;
		ve.pb(r);
		ve.pb(p);
		while(p!=r){
			p=oya[p];
			ve.pb(p);
		}
		ve.pop_back();
		bo=false;
		return;
	}
	vis[r]=1;
	bi[r]=val;
	oya[r]=p;
	for(auto v:G[r]){
		dfs(v.first,1-val,r);
		if(!bo) return;
	}
	return;
}


    signed main(){
               cin.tie(0);
    		ios::sync_with_stdio(false);
cin>>n>>m;
    	
    	for(int i=0;i<m;i++){
    		int y,yy,yyy;
    		cin>>y>>yy>>yyy;
    		G[y].pb(mp(yy,yyy));
    		G[yy].pb(mp(y,yyy));
    		maa[mp(y,yy)]=yyy;
    		maa[mp(yy,y)]=yyy;
    	}
    	for(int i=1;i<=n;i++)hai[i]=-1;
    	dfs_bi(1,0,1);
   	bool nibu=1;
    	for(int i=1;i<=n;i++){
    		for(auto v:G[i])if(hai[i]+hai[v.first]!=1)nibu=0;
    	}
    	
    	if(nibu){
    		dfs_vis(1,0,1);
    		
    		for(int i=1;i<=n;i++){
    			for(auto v:G[i])if(atai[i]+atai[v.first]!=v.second){
    				cout<<0<<endl;
    				return 0;
    			}
    		}
    		int ma1=-ma,ma0=-ma,mi1=ma,mi0=ma;
    		for(int i=1;i<=n;i++){
    			if(hai[i]==1){
    				ma1=max(ma1,atai[i]);
    				mi1=min(mi1,atai[i]);
    			}
    			else{
    			ma0=max(ma0,atai[i]);
    				mi0=min(mi0,atai[i]);
    			}
    		}
    		ma1-=mi0-1;
    		mi1+=mi0-1;
    		ma1+=mi0-1;
    		mi0=1;
    		
    		cout<<max(0ll,mi1)<<endl;
    		return 0;
    	}
    	//cout<<"d"<<endl;
    	dfs(1,0,1);
    	int wasum=0;
    	int l=ve.size();
    	//cout<<l<<endl;
    	for(int i=0;i<l;i++){
    		wasum+=maa[mp(ve[i],ve[(i+1)%l])];
    	//	cout<<ve[i]<<" "<<ve[(i+1)%l]<<" "<<maa[mp(ve[i],ve[(i+1)%l])]<<endl;
    	}
    	if(wasum%2){
    		cout<<0<<endl;
    		return 0;
    	}
    	wasum/=2;
    	
    	for(int i=1;i<l;i+=2){
    		wasum-=maa[mp(ve[i],ve[i+1])];
    	}
    	atai[ve[0]]=wasum;
    	
    	for(int i=1;i<=n;i++)vis[i]=0;
    	dfs_vis(ve[0],wasum,ve[0]);
    	for(int i=1;i<=n;i++){
    		if(atai[i]<=0) {
    			cout<<0<<endl;
    			return 0;
    		}
    			for(auto v:G[i])if(atai[i]+atai[v.first]!=v.second){
    				cout<<0<<endl;
    				return 0;
    			}
    	}
    	cout<<1<<endl;
    	return 0;
            }


Measured memory_bytes: 26624