#include <bits/stdc++.h>

using namespace std;

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

vector <int> v[360];
queue <int> q;
priority_queue < pair < int , int >  , vector < pair < int , int > > , greater < pair < int , int > > > h;
int n,s,d,cost_min,min_dist[360],new_dist[360],dist[360],tata[360],flux[360][360],cost[360][360],C[360][360];

void Bellman_Ford()
{
    int i,nod;

    for(i=1;i<=n;i++)dist[i]=INT_MAX/2;
    dist[s]=0;q.push(s);

    while(!q.empty())
    {
        nod=q.front();
        q.pop();

        for(i=0;i<v[nod].size();i++)
        {
            int vecin=v[nod][i];
            if(flux[nod][vecin]<C[nod][vecin] && dist[vecin]>dist[nod]+cost[nod][vecin])
            {
                dist[vecin]=dist[nod]+cost[nod][vecin];
                q.push(vecin);
            }
        }
    }
}

int Dijkstra()
{
    int i,nod,flux_min=INT_MAX;

    for(i=1;i<=n;i++)min_dist[i]=INT_MAX/2,tata[i]=-1;

    new_dist[s]=0;min_dist[s]=0;h.push({0,s});
    while(!h.empty())
    {
        int nod=h.top().second;
        int dst=h.top().first;
        h.pop();

        if(dst<=min_dist[nod])
        {
            for(i=0;i<v[nod].size();i++)
            {
                int vecin=v[nod][i];
                int dist_intre=cost[nod][vecin]+dist[nod]-dist[vecin];
                if(flux[nod][vecin] < C[nod][vecin] && min_dist[vecin]>min_dist[nod]+dist_intre)
                {
                    min_dist[vecin]=min_dist[nod]+dist_intre;
                    new_dist[vecin]=cost[nod][vecin] + new_dist[nod];
                    tata[vecin]=nod;
                    h.push({min_dist[vecin],vecin});
                }
            }
        }
    }

    if(min_dist[d]==INT_MAX/2)return false;

    nod=d;
    while(tata[nod]!=-1)
    {
        flux_min=min(flux_min,C[tata[nod]][nod]-flux[tata[nod]][nod]);
        nod=tata[nod];
    }

    nod=d;
    while(tata[nod]!=-1)
    {
        flux[tata[nod]][nod]+=flux_min;
        flux[nod][tata[nod]]-=flux_min;
        nod=tata[nod];
    }

    cost_min+=flux_min*new_dist[d];

    for(i=1;i<=n;i++)
        dist[i]=new_dist[i];
    return true;
}

int m,i,x,y,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);
        v[y].push_back(x);
        C[x][y]=c;
        cost[x][y]=z;cost[y][x]=-z;
    }

    Bellman_Ford();
    while(Dijkstra());
    g<<cost_min;
    return 0;
}