let n = readLine()!.split(separator: " ").map{Int($0)!}
let d = (n[0] + 1) * n[1]
var a = 0.0
for i in 0...n[0]{
    for _ in 1...n[1]{
        a += 1.0 / Double(d) * Double(i)
    }
}
print(a)