//set many funcs template
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<stdbool.h>
#include<time.h>
#define inf 1072114514
#define llinf 4154118101919364364
#define mod 1000000007
#define pi 3.1415926535897932384

int max(int a,int b){if(a>b){return a;}return b;}
int min(int a,int b){if(a<b){return a;}return b;}
int zt(int a,int b){return max(a,b)-min(a,b);}
int round(int a,int b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
int ceil(int a,int b){if(a%b==0){return a/b;}return (a/b)+1;}
int gcd(int a,int b){int c;while(b!=0){c=a%b;a=b;b=c;}return a;}
int lcm(int a,int b){int c=gcd(a,b);a/=c;return a*b;}
int nCr(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
int nHr(int a,int b){return nCr(a+b-1,b);}
int fact(int a){int i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
int pow(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
int dsum(int x){int r=0;while(x){r+=(x%10);x/=10;}return r;}
int dsumb(int x,int b){int r=0;while(x){r+=(x%b);x/=b;}return r;}
int sankaku(int x){return ((1+x)*x)/2;}
long long llmax(long long a,long long b){if(a>b){return a;}return b;}
long long llmin(long long a,long long b){if(a<b){return a;}return b;}
long long llzt(long long a,long long b){return llmax(a,b)-llmin(a,b);}
long long llround(long long a,long long b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
long long llceil(long long a,long long b){if(a%b==0){return a/b;}return (a/b)+1;}
long long llgcd(long long a,long long b){long long c;while(b!=0){c=a%b;a=b;b=c;}return a;}
long long lllcm(long long a,long long b){long long c=llgcd(a,b);a/=c;return a*b;}
long long llnCr(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
long long llnHr(long long a,long long b){return llnCr(a+b-1,b);}
long long llfact(long long a){long long i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
long long llpow(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
long long lldsum(long long x){long long r=0;while(x){r+=(x%10);x/=10;}return r;}
long long lldsumb(long long x,long long b){long long r=0;while(x){r+=(x%b);x/=b;}return r;}
long long llsankaku(long long x){return ((1+x)*x)/2;}
double dbmax(double a,double b){if(a>b){return a;}return b;}
double dbmin(double a,double b){if(a<b){return a;}return b;}
double dbzt(double a,double b){return dbmax(a,b)-dbmin(a,b);}
int sortfncsj(const void *a,const void *b){if(*(int *)a>*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int sortfnckj(const void *a,const void *b){if(*(int *)a<*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int llsortfncsj(const void *a,const void *b){if(*(long long *)a>*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int llsortfnckj(const void *a,const void *b){if(*(long long *)a<*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int dbsortfncsj(const void *a,const void *b){if(*(double *)a>*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int dbsortfnckj(const void *a,const void *b){if(*(double *)a<*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int strsortfncsj(const void *a,const void *b){return strcmp((char *)a,(char *)b);}
int strsortfnckj(const void *a,const void *b){return strcmp((char *)b,(char *)a);}

typedef struct{
long long node;
long long ki;
long long co;
long long kr;
}data;

data q[1048576];
long long qp=0,qqp=0;

void qpush(data x){
    qp++;q[qp]=x;
}

data qpop(){
    qqp++;
    return q[qqp];
}

void shuffledget(int x[],int n){
    srand(time(0));
    int i,b[524288],p,c;
    for(i=0;i<n;i++){
        b[i]=i;
    }
    for(i=n;i>=1;i--){
        p=rand()%i;
        c=b[i-1];b[i-1]=b[p];b[p]=c;
    }
    for(i=0;i<n;i++){
        scanf("%d",&x[b[i]]);
    }
}

typedef struct{
    long long st;
    long long fi;
    long long kr;
}rs;

typedef struct{
    long long st;
    long long kz;
}mkj;

int sortfnc(const void *a,const void *b){
if(((rs*)a)->st == ((rs*)b)->st){return 0;}
if(((rs*)a)->st < ((rs*)b)->st){return -1;}
return 1;
}

void makemkj(rs g[],mkj x[],long long n){
    long long i,ms=0,nst=g[0].st;
    for(i=1;i<n;i++){
        if(g[i].st!=g[i-1].st){
            x[nst].kz=i-ms;
            x[nst].st=ms;
            nst=g[i].st;ms=i;
        }
    }
    x[nst].kz=n-ms;
    x[nst].st=ms;
}

int main(void){
    long long i,j,n,m,k,a,b,c,w,r=llinf,l,t,nv;
    double d;
    rs g[262144];
    mkj x[262144];
    char s[524288];
    data pd,od;
    long long aki[262144],aco[262144],lb=1,ub=llinf;
    scanf("%lld%lld",&n,&m);
    //l=strlen(s);
    for(i=0;i<m;i++){
        scanf("%lld%lld%lld",&a,&b,&c);
        g[2*i].st=a;g[2*i].fi=b;g[2*i].kr=c;
        g[2*i+1].st=b;g[2*i+1].fi=a;g[2*i+1].kr=c;
    }
    for(i=0;i<=n;i++){aki[i]=-1;}
    qsort(g,2*m,sizeof(rs),sortfnc);
    makemkj(g,x,2*m);
    pd.node=1;pd.ki=1;pd.co=0;pd.kr=0;
    qpush(pd);
    while(qp-qqp){
        od=qpop();
        nv=od.node;
        if(od.ki==1){
            if(aki[nv]==-1){
                aki[nv]=0;
                aco[nv]=od.kr-od.co;
                lb=llmax(lb,1+od.co-od.kr);
                pd.ki=0;pd.co=aco[nv];
                for(i=x[nv].st;i<x[nv].st+x[nv].kz;i++){
                    pd.node=g[i].fi;
                    pd.kr=g[i].kr;
                    qpush(pd);
                }
            }
            else if(aki[nv]==0){
                if(aco[nv]!=od.kr-od.co){
                    lb=llinf;ub=-100;
                }
            }
            else{
                k=aco[nv]-(od.kr-od.co);
                if(k%2==1){lb=llinf;ub=-100;}
                lb=llmax(lb,k/2);ub=llmin(ub,k/2);
            }
        }
        else{
            if(aki[nv]==-1){
                aki[nv]=1;
                aco[nv]=od.kr-od.co;
                ub=llmin(ub,od.kr-od.co-1);
                pd.ki=1;pd.co=aco[nv];
                for(i=x[nv].st;i<x[nv].st+x[nv].kz;i++){
                    pd.node=g[i].fi;
                    pd.kr=g[i].kr;
                    qpush(pd);
                }
            }
            else if(aki[nv]==1){
                if(aco[nv]!=od.kr-od.co){
                    lb=llinf;ub=-100;
                }
            }
            else{
                k=(od.kr-od.co)-aco[nv];
                if(k%2==1){lb=llinf;ub=-100;}
                lb=llmax(lb,k/2);ub=llmin(ub,k/2);
            }
        }
    }
    printf("%lld\n",llmax(0,ub-lb+1));
    return 0;
}

Measured memory_bytes: 21420