#include<cstdio>
#include<vector>
#include<cstring>
#include<queue>
#define INF 20000000000
using namespace std;
vector<int>L[500];
queue<int>q;
int n,cost,m,s,dr,a,b,ab,cc,i,j,vmin,ih,c[500][500],w[500][500],x[500][500],v[500],d[500],e[500],t[500],h[500],P[500],r[500],dh,poz;
FILE *f,*g;
int minim(int a,int b){
    if(a<b)
        return a;
    return b;
}
void bf(){
    q.push(s);
    v[s]=1;
    for(int i=1;i<=n;i++){
        d[i]=INF;
    }
    d[s]=0;
    while(!q.empty()){
        a=q.front();
        q.pop();
        v[a]=0;
        for(int i=0;i<L[a].size();i++){
            if(d[ L[a][i] ]>d[a]+x[a][ L[a][i] ] &&c[a][ L[a][i] ] > w[a][ L[a][i] ]){
                d[ L[a][i] ]=d[a]+x[a][ L[a][i] ] ;
                if(v[ L[a][i] ]==0){
                    v[ L[a][i] ]=1;
                    q.push(L[a][i]);
                }
            }
        }
    }
}
void chg(int &a,int &b){
    int aux=a;
    a=b;
    b=aux;
}
void del(){
    h[1]=h[dh];
    dh--;
    P[h[1]]=1;
    int p=1;
    int c=2;
    while(c<=dh){
        if(c<dh&&e[ h[c] ]>e[ h[c+1] ])
            c++;
        if(e[h[c]]<e[h[p]]){
            chg(h[p],h[c]);
            P[ h[p] ]=p;
            P[ h[c] ]=c;
            p=c;
            c*=2;
        }
        else
            break;
    }
}
void upd(int poz){
    int c=poz;
    int p=poz/2;
    while(p>=1){
        if(e[h[c]]<e[h[p]]){
            chg(h[p],h[c]);
            P[ h[p] ]=p;
            P[ h[c] ]=c;
            c=p;
            p/=2;
        }
        else
            break;
    }
}
int dijkstra(){
    memset(t,0,sizeof(t));
    for(i=1;i<=n;i++){
        e[i]=INF;
    }
    e[s]=r[s]=0;
    h[1]=s;
    dh=1;
    P[s]=1;
    int ok=0;
    while(dh){
        poz=h[1];
        del();
        for(i=0;i<L[poz].size();i++){
            a=L[poz][i];
            if(e[a]>e[poz]+x[poz][a]-d[a]+d[poz]&&c[poz][a]>w[poz][a]){
                t[a]=poz;
                if(a==dr)
                    ok=1;
                if(e[a]==INF)
                    ih=0;
                else
                    ih=1;
                e[a]=e[poz]-d[a]+d[poz]+x[poz][a];
                r[a]=r[poz]+x[poz][a];
                if(ih==0){
                    h[++dh]=a;
                    P[ h[dh] ]=dh;
                    upd(dh);
                }
                else
                    upd(P[a]);
            }
        }
    }
    return ok;
}
int main(){
    f=fopen("fmcm.in","r");
    g=fopen("fmcm.out","w");
    fscanf(f,"%d%d%d%d",&n,&m,&s,&dr);
    for(i=1;i<=m;i++){
        fscanf(f,"%d%d%d%d",&a,&b,&ab,&cc);
        L[a].push_back(b);
        L[b].push_back(a);
        c[a][b]=ab;
        x[a][b]=cc;
        x[b][a]=-cc;
    }
    bf();
    while(dijkstra()){
        vmin=INF;
        a=dr;
        do{
            vmin=minim(vmin,c[ t[a] ][a]-w[ t[a] ][a]);
            a=t[a];
        }while(a!=s);
        if(vmin){
            a=dr;
            do{
                w[ t[a] ][a]+=vmin;
                w[a][ t[a] ]-=vmin;
                a=t[a];
            }while(a!=s);
        }
        cost+=(vmin*r[dr]);
    }
    fprintf(g,"%d",cost);

    fclose(f);
    fclose(g);
    return 0;
}