#include <stdio.h>
#include <vector>

using namespace std;

vector<int> graf[355];
vector<int>::iterator u;
int i,n,m,s,d,x,y,c,z,heap[355],poz[355],aux,first,difmin[355],cap[355][355],f[355][355],cost[355][355],tt[355];
long long dist[355],sol;
bool k;

inline void heap_up(int p)
{
	while (p>1 && dist[heap[p]]<dist[heap[p>>1]])
	{
		aux=heap[p];
		heap[p]=heap[p>>1];
		heap[p>>1]=aux;
		poz[heap[p]]=p;
		poz[heap[p>>1]]=p>>1;
		p>>=1;
	}
}

inline void heap_down(int p)
{
	int min;
	while ((p*2<=x && dist[heap[p]]>dist[heap[p*2]]) || (p*2+1<=x && dist[heap[p]]>dist[heap[p*2+1]]))
	{
		if (p*2+1<=x)
			if (dist[heap[p*2]]<dist[heap[p*2+1]])
				min=p*2;
			else
				min=p*2+1;
		else
			min=p*2;
		aux=heap[p];
		heap[p]=heap[min];
		heap[min]=aux;
		poz[heap[p]]=p;
		poz[heap[min]]=min;
		p=min;
	}
}

int main()
{
	freopen("fmcm.in","r",stdin);
	freopen("fmcm.out","w",stdout);
	scanf("%d %d %d %d",&n,&m,&s,&d);
	for (i=1;i<=m;++i)
	{
		scanf("%d %d %d %d",&x,&y,&c,&z);
		graf[x].push_back(y);
		cap[x][y]=c;
		cost[x][y]=z;
		graf[y].push_back(x);
		cost[y][x]=-z;
	}
	k=true;
	while (k)
	{
		k=false;
		poz[1]=0;
		dist[1]=1LL*13000*10000000;
		for (i=2;i<=n;++i)
		{
			poz[i]=0;
			dist[i]=dist[i-1];
		}
		x=1;
		heap[1]=s;
		poz[s]=1;
		dist[s]=0;
		difmin[s]=2147000000;
		while (x)
		{
			first=heap[1];
			if (first==d)
				k=true;
			poz[heap[1]]=0;
			if (x==1)
				x=0;
			else
			{
				heap[1]=heap[x--];
				poz[heap[1]]=1;
				heap_down(1);
			}
			for (u=graf[first].begin();u!=graf[first].end();++u)
				if (cap[first][*u]>f[first][*u] && dist[first]+cost[first][*u]<dist[*u])
				{
					if (difmin[first]<cap[first][*u]-f[first][*u])
						difmin[*u]=difmin[first];
					else
						difmin[*u]=cap[first][*u]-f[first][*u];
					dist[*u]=dist[first]+cost[first][*u];
					tt[*u]=first;
					if (poz[*u])
						heap_up(poz[*u]);
					else
					{
						heap[++x]=*u;
						poz[heap[x]]=x;
						heap_up(x);
					}
				}
		}
		if (k)
			for (i=d;i!=s;i=tt[i])
			{
				f[tt[i]][i]+=difmin[d];
				f[i][tt[i]]-=difmin[d];
				sol+=difmin[d]*cost[tt[i]][i];
			}
	}
	printf("%lld",sol);
	return 0;
}