#include <iostream>

#include <fstream>

#include <vector>

#include <cstring>

using namespace std;

ifstream fin("sate.in");

ofstream fout("sate.out");

struct muchie{

  int x,c;

};

vector <muchie> v[30001];

int a,b,n,m,x,y,k1,k2,q[90000001],viz[30001],j,S,i,d,ns;

char s[1001];

void coada(int x){

    int p,u,i,l;

    p=u=1;

    q[p]=x;

    viz[x]=1;

    while(p<=u){

        l=q[p];

        p++;

        for(i=0;i<v[l].size();i++)

            if(viz[v[l][i].x]==0)

                if(v[l][i].x!=y){

                u++;

                q[u]=v[l][i].x;

                if(v[l][i].x<l)

                    viz[v[l][i].x]=viz[l]-v[l][i].c;

                else

                    viz[v[l][i].x]=viz[l]+v[l][i].c;



            }

            else{

                if(v[l][i].x==y)

                    if(v[l][i].x<l)

                    viz[v[l][i].x]=viz[l]-v[l][i].c;

                else

                    viz[v[l][i].x]=viz[l]+v[l][i].c;

                 p=u+1;

                 break;

            }}}

int main()

{

    fin.getline(s,999);

	ns=strlen(s);

	n=s[0]-'0';

	i=1;

	while(s[i]>='0'&&s[i]<='9'){

		n=n*10+(s[i]-'0');

		i++;}

	i++;

	m=s[i]-'0';

	i++;

	while(s[i]>='0'&&s[i]<='9'){

		m=m*10+(s[i]-'0');

		i++;}

	i++;

	x=s[i]-'0';

	i++;

	while(s[i]>='0'&&s[i]<='9'){

		x=x*10+(s[i]-'0');

		i++;}

	i++;

	y=s[i]-'0';

	i++;

	while(s[i]>='0'&&s[i]<='9'&&i<ns){

		y=y*10+(s[i]-'0');

		i++;}

	for(i=1;i<=m;i++){

		fin.getline(s,999);

		ns=strlen(s);

		a=s[0]-'0';

		j=1;

		while(s[j]>='0'&&s[j]<='9'){

			a=a*10+(s[j]-'0');

			j++;

		}

		j++;

		b=s[j]-'0';

		j++;

		while(s[j]>='0'&&s[j]<='9'){

			b=b*10+(s[j]-'0');

			j++;

		}

		j++;

		d=s[j]-'0';

		j++;

		while(s[j]>='0' && s[j]<='9' && j<ns)

		{

			d=d*10+(s[j]-'0');

			j++;

		}

       v[a].push_back({b,d});

       v[b].push_back({a,d});

    }

    S=0;

 coada(x);

 viz[y]--;

    fout<<viz[y];

    return 0;

}