import itertools N, M = map(int, input().split()) P = list(map(int, input().split())) A = [] B = [] C = [] for n in range(N-1): a,b,c = map(int, input().split()) A.append(a) B.append(b) C.append(c) imos = [0] * N for m in range(M-1): if P[m] < P[m+1]: imos[P[m]-1] += 1 imos[P[m+1]-1] -= 1 else: imos[P[m]-1] -= 1 imos[P[m+1]-1] += 1 csum = list(itertools.accumulate(imos)) ans = 0 for n in range(N-1): cnt = csum[n] ans += min(A[n]*cnt, B[n]*cnt+C[n]) print (ans)umulate(imos)) print (max(csum))