#include <bits/stdc++.h>

using namespace std;

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

vector < pair < int , int > > v[351];
queue <int> q;
priority_queue < pair < int , int > , vector < pair < int , int > > , greater < pair < int , int > > > h;
int ans,n,S,D,tata[351],cost_dijk[351],new_cost_bell[351],cost_bell[351],inCoada[351],C[351][351],flux[351][351];

void Bellman_Ford()
{
    int i;
    for(i=1;i<=n;i++)cost_bell[i]=INT_MAX/2;
    cost_bell[S]=0;q.push(S);inCoada[S]=1;
    while(!q.empty())
    {
        int nod=q.front();
        q.pop();
        inCoada[nod]=0;

        for(i=0;i<v[nod].size();i++)
        {
            int vecin=v[nod][i].first;
            int cost_intre=v[nod][i].second;
            if(cost_bell[vecin]>cost_bell[nod]+cost_intre && C[nod][vecin]>0)
            {
                cost_bell[vecin]=cost_bell[nod]+cost_intre;
                if(inCoada[vecin]==0)
                {
                    q.push(vecin);
                    inCoada[vecin]=1;
                }
            }
        }
    }
}

int Dijkstra()
{
    int i;
    for(i=1;i<=n;i++)cost_dijk[i]=INT_MAX/2,new_cost_bell[i]=INT_MAX/2,tata[i]=0;
    cost_dijk[S]=0;h.push({0,S});new_cost_bell[S]=0;

    while(!h.empty())
    {
        int nod=h.top().second;
        int cst=h.top().first;
        h.pop();

        if(cst>cost_dijk[nod])continue;

        for(i=0;i<v[nod].size();i++)
        {
            int vecin=v[nod][i].first;
            int cost_intre=v[nod][i].second+cost_bell[nod]-cost_bell[vecin];

            if(flux[nod][vecin]<C[nod][vecin] && cost_dijk[vecin]>cost_dijk[nod]+cost_intre)
            {
                cost_dijk[vecin]=cost_dijk[nod]+cost_intre;
                new_cost_bell[vecin]=new_cost_bell[nod]+v[nod][i].second;
                tata[vecin]=nod;

                h.push({cost_dijk[vecin],vecin});
            }
        }
    }

    if(cost_dijk[D]==INT_MAX/2)return 0;

    int min_flow=C[tata[D]][D]-flux[tata[D]][D];
    int nod=tata[D];
    while(tata[nod]!=0)
    {
        min_flow=min(min_flow,C[tata[nod]][nod]-flux[tata[nod]][nod]);
        nod=tata[nod];
    }

    ans+=min_flow*new_cost_bell[D];

    nod=D;
    while(tata[nod]!=0)
    {
        flux[tata[nod]][nod]+=min_flow;
        flux[nod][tata[nod]]-=min_flow;
        nod=tata[nod];
    }

    for(int i=1;i<=n;i++)cost_bell[i]=new_cost_bell[i];
    return 1;
}

int m,x,y,i,c,z;
int main()
{
    f>>n>>m>>S>>D;
    for(i=1;i<=m;i++)
    {
        f>>x>>y>>c>>z;
        v[x].push_back({y,z});
        v[y].push_back({x,-z});
        C[x][y]=c;
    }

    Bellman_Ford();
    while(Dijkstra());

    g<<ans;
    return 0;
}