#include <bits/stdc++.h>

const int oo=1e9;

using namespace std;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

int n,m,s,D,i,j,fluxmax,dist[360],C[360][360],cap[360][360];
vector<int> v[360];

void bellman()
{
    bool in[n+2];
    for(i=1;i<=n;i++)
        dist[i]=oo,in[i]=0;
    dist[s]=0;in[s]=1;
    deque<int> q;q.resize(0);
    q.push_back(s);
    while(q.size())
    {
        int x=q.front();
        q.pop_front();
        in[x]=0;
        for(auto it:v[x])
            if(dist[it]>dist[x]+C[x][it])
            {
                dist[it]=dist[x]+C[x][it];
                if(!in[it])
                    q.push_back(it);
                in[it]=1;
            }
    }
    return ;
}

bool djikstra()
{
    priority_queue<pair<int,int> > q;
    int d[360],real_d[360],tata[360];
    for(i=1;i<=n;i++)
        d[i]=real_d[i]=oo,tata[i]=0;
    real_d[s]=d[s]=0;tata[s]=-1;
    q.push({0,s});
    while(q.size())
    {
        int x=q.top().second,cost=q.top().first;
        q.pop();
        if(cost!=d[x])
            continue;
        for(auto it:v[x])
            if(cap[x][it])
            {
                int new_d=d[x]+C[x][it]+dist[it]-dist[x];
                if(new_d<d[it])
                {
                    d[it]=new_d;
                    tata[it]=x;
                    real_d[it]=real_d[x]+C[x][it];
                    q.push({d[it],it});
                }
            }
    }
    for(i=1;i<=n;i++)
        dist[i]=real_d[i];
    if(d[D]==oo)
        return 0;
    int x=D,flux=oo;
    while(x!=s)
    {
        x=tata[x];
        flux=min(flux,cap[x][tata[x]]);
    }
    x=D;
    while(x!=s)
    {
        x=tata[x];
        cap[x][tata[x]]-=flux;
        cap[tata[x]][x]+=flux;
    }
    fluxmax+=flux*dist[D];
}

int main()
{
    f>>n>>m>>s>>D;
    for(i=1;i<=m;i++)
    {
        int x,y,c,z;
        f>>x>>y>>c>>z;
        v[x].push_back(y);
        v[y].push_back(x);
        cap[x][y]=c;
        C[x][y]=z;
        C[y][x]=-z;
    }
    bellman();
    for(;djikstra(););
    g<<fluxmax;
    return 0;
}