from sys import stdin
input = stdin.readline
n, m = [int(x) for x in input().split()]
a = [int(x) for x in input().split()]
ans = 0
for _ in range(m):
u, v, w = [int(x) for x in input().split()]
ans = max(ans, (a[u-1]+a[v-1])/w)
print(ans)
1370A - Maximum GCD | 149A - Business trip |
34A - Reconnaissance 2 | 59A - Word |
462B - Appleman and Card Game | 1560C - Infinity Table |
1605C - Dominant Character | 1399A - Remove Smallest |
208A - Dubstep | 1581A - CQXYM Count Permutations |
337A - Puzzles | 495A - Digital Counter |
796A - Buying A House | 67A - Partial Teacher |
116A - Tram | 1472B - Fair Division |
1281C - Cut and Paste | 141A - Amusing Joke |
112A - Petya and Strings | 677A - Vanya and Fence |
1621A - Stable Arrangement of Rooks | 472A - Design Tutorial Learn from Math |
1368A - C+= | 450A - Jzzhu and Children |
546A - Soldier and Bananas | 32B - Borze |
1651B - Prove Him Wrong | 381A - Sereja and Dima |
41A - Translation | 1559A - Mocha and Math |