// O(N^2 * M^2)
#include <fstream>
#include <vector>
#include <queue>
#include <cstring>
#define Nmax 355
#define oo 2000000000
#define pb push_back
using namespace std;
ifstream f("fmcm.in");
ofstream g("fmcm.out");

int N,M,Source,Sink,x,y,c,z,MaxFlow,CostMin;
int cap[Nmax][Nmax],cost[Nmax][Nmax],flow[Nmax][Nmax],ante[Nmax],d[Nmax],old_d[Nmax],real_d[Nmax];
vector < int > G[Nmax];

typedef pair<int,int> PP;
priority_queue < PP  , vector < PP > , greater<PP> > pq;

inline void ReadInput()
{
    f>>N>>M>>Source>>Sink;
    for(int i=1;i<=M;++i)
        {
            f>>x>>y>>c>>z;
            G[x].pb(y) , G[y].pb(x);
            cap[x][y]=c;
            cost[x][y]=z , cost[y][x]=-z;
        }
}

int Dijkstra(int Source)
{
    for(int i=1;i<=N;++i)d[i]=oo,ante[i]=oo;
    d[Source]=0 , ante[Source]=Source;
    for(pq.push(PP(0,Source)); !pq.empty();)
    {
        int node=pq.top().second, val=pq.top().first;
        pq.pop();
        if(d[node]!=val)continue;
        for(vector<int>::iterator it=G[node].begin();it!=G[node].end();++it)
            if(flow[node][*it]<cap[node][*it])
            {
                int aux=d[node]+cost[node][*it]+old_d[node]-old_d[*it];
                if(aux<d[*it])
                {
                    ante[*it] = node;
                    d[*it] = aux;
                    real_d[*it] = real_d[node] + cost[node][*it];
                    pq.push( PP(d[*it] , *it) );
                }
            }
    }
    memcpy( old_d, real_d, sizeof( old_d ) );
    return (d[Sink]!=oo) ;
}

void GetFMCM()
{
    for( ; Dijkstra(Source) ; )
    {
        int MinFlow=oo;
        for(int i=Sink; i!=Source ; i=ante[i])
            MinFlow=min(MinFlow,cap[ante[i]][i]-flow[ante[i]][i]);
        if(MinFlow)
        {
            for(int i=Sink; i!=Source ; i=ante[i])
            {
                flow[ante[i]][i]+=MinFlow;
                flow[i][ante[i]]-=MinFlow;
            }
            MaxFlow+=MinFlow;
            CostMin+=MinFlow*real_d[Sink];
        }
    }
    g<<CostMin<<'\n';
}

int main()
{
    ReadInput();
    GetFMCM();
    f.close();g.close();
    return 0;
}