#include <iostream>
#include <fstream>
#include <vector>
#include <climits>
#include <cstring>
using namespace std;

int n, s, t;
int doo[102], part[102], query[102];
int smegnost[102][102], f[102][102];

bool bfs() {
    int qh = 0, qt = 0;
    query[qt++] = s;
    memset(doo, -1, n * sizeof doo[0]);
    doo[s] = 0;
    while (qh < qt) {
        int v = query[qh++];
        for (auto i = 0; i < n; ++i)
            if (doo[i] == -1 && f[v][i] < smegnost[v][i]){
                query[qt++] = i;
                doo[i] = doo[v] + 1;
            }
    }
    return doo[t] != -1;
}

int dfs (int v, int flow) {
    if (!flow)  return 0;
    if (v == t)  return flow;
    int x = part[v];
    for (auto i = x; i < n; ++i) {
        if (doo[i] != doo[v] + 1)  continue;
        int push = dfs(i, min(flow, smegnost[v][i] - f[v][i]));
        if (push) {
            f[v][i] += push;
            f[i][v] -= push;
            return push;
        }
    }
    return 0;
}

int main(){
    ifstream fin("circulation.in");
    ofstream fout("circulation.out");
    int m;
    fin >> n >> m;
    n = n + 1;
     for(auto i = 0; i < m; ++i){
        int x, y, z, q;
        fin >> x >> y >> z >> q;
        if(z == 0)
            smegnost[x][y] = q;
        else{
            smegnost[0][y] = z;
            smegnost[x][n] = z;
            smegnost[x][y] = q - z;
            }
        }
    s = 0; t = n - 1;
    int foo = 0;
    for (;;) {
        if (!bfs())  break;
        memset(part, 0, n * sizeof part[0]);
        while (int push = dfs(s, INT_MAX)) foo += push;
    }
    fout << foo;
    return 0;
    }