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

#define maxN 355
#define INF 0x3f3f3f3f

using namespace std;

FILE*f=fopen("fmcm.in","r");
FILE*g=fopen("fmcm.out","w");

int n,m,S,D,i,x,y,c,z,C[maxN],FlowCost;
short int Cp[maxN][maxN],F[maxN][maxN],T[maxN]; int minim;
int qsize,nod,nodvcn; bool inQ[maxN];

vector< pair<short int,short int> >G[maxN]; 
queue<short int>Q;

inline void citire () {
	
	fscanf(f,"%d %d %d %d",&n,&m,&S,&D);
	
	for ( i = 1 ; i <= m ; ++i ){
		fscanf(f,"%d %d %d %d",&x,&y,&c,&z);
		G[x].push_back( make_pair(y,z) );
		G[y].push_back( make_pair(x,-z) );
		Cp[x][y] = c;
	}
}

inline void init () {
	
	memset(inQ,0,sizeof(inQ));
	memset(C,INF,sizeof(C));
	
	C[S] = 0; minim = INF;
	Q.push(S); qsize = 1; inQ[S] = 1;
}

inline bool bellmanford () {
	
	init(); vector< pair<short int,short int> >::iterator itt;
	
	while ( qsize ){
		
		nod = Q.front(); Q.pop(); --qsize; inQ[nod] = 0;
		
		for ( itt = G[nod].begin() ; itt != G[nod].end() ; ++itt ){
			nodvcn = itt->first;
			if ( Cp[nod][nodvcn] > F[nod][nodvcn] && C[nodvcn] > C[nod] + itt->second ){
				C[nodvcn] = C[nod] + itt->second; T[nodvcn] = nod;
				if ( !inQ[nodvcn] ){
					inQ[nodvcn] = 1;
					Q.push(nodvcn); ++qsize;
				}
			}
		}
	}
	
	if ( C[D] != INF ){
		
		for ( nod = D ; T[nod]; nod = T[nod] ){
			minim = Cp[T[nod]][nod] - F[T[nod]][nod] < minim ? Cp[T[nod]][nod] - F[T[nod]][nod] : minim;
		}
		for ( nod = D ; T[nod] ; nod = T[nod] ){
			F[T[nod]][nod] += minim;
			F[nod][T[nod]] -= minim;
		}
	}
	
	return (C[D] != INF);
}

inline void fmcm () {
	
	while ( bellmanford() ){
		FlowCost += minim * C[D];
	}
	
	fprintf(g,"%d\n",FlowCost);
}

int main () {
	
	citire();
	fmcm();
	
	fclose(f);
	fclose(g);
	
	return 0;
}