# Reference: https://tjkendev.github.io/procon-library/python/min_cost_flow/primal-dual.html from heapq import heappush, heappop class MinCostFlow: INF = 10**18 def __init__(self, N): self.N = N self.G = [[] for i in range(N)] def add_edge(self, fr, to, cap, cost): forward = [to, cap, cost, None] backward = forward[3] = [fr, 0, -cost, forward] self.G[fr].append(forward) self.G[to].append(backward) def flow(self, s, t, f): N = self.N; G = self.G INF = MinCostFlow.INF res = 0 H = [0]*N prv_v = [0]*N prv_e = [None]*N d0 = [INF]*N dist = [INF]*N while f: dist[:] = d0 dist[s] = 0 que = [(0, s)] while que: c, v = heappop(que) if dist[v] < c: continue r0 = dist[v] + H[v] for e in G[v]: w, cap, cost, _ = e if cap > 0 and r0 + cost - H[w] < dist[w]: dist[w] = r = r0 + cost - H[w] prv_v[w] = v; prv_e[w] = e heappush(que, (r, w)) if dist[t] == INF: return None for i in range(N): H[i] += dist[i] d = f; v = t while v != s: d = min(d, prv_e[v][1]) v = prv_v[v] f -= d res += d * H[t] v = t while v != s: e = prv_e[v] e[1] -= d e[3][1] += d v = prv_v[v] return res def main(): n, m = map(int, input().split()) mf = MinCostFlow(n) for _ in range(m): u, v, c, d = map(int, input().split()) mf.add_edge(u-1, v-1, 1, c) mf.add_edge(u-1, v-1, 1, d) mf.add_edge(v-1, u-1, 1, c) mf.add_edge(v-1, u-1, 1, d) print(mf.flow(0, n-1, 2)) main()