```go
package main

import (
    "fmt"
)

func main() {
    var n, m int
    fmt.Scan(&n, &m)
    
    x := make([]int64, n)
    for i := 0; i < n; i++ {
        fmt.Scan(&x[i])
    }
    
    var ans float64
    for i := 0; i < m; i++ {
        var a, b int
        var c int64
        fmt.Scan(&a, &b, &c)
        a--
        b--
        d := float64(x[a] + x[b] + c)
        if d > ans {
            ans = d
        }
    }
    
    fmt.Printf("%.9f\n", ans)
}
```