let inputs = readLine()!.split(separator: " ")
let A = Int(inputs[0])!
let Bs = Array(inputs[1])
let base = Character("0").unicodeScalars.first!.value
let B = 100 * Int(Bs[0].unicodeScalars.first!.value - base) +
        10 * Int(Bs[2].unicodeScalars.first!.value - base) +
        Int(Bs[3].unicodeScalars.first!.value - base)     
print(A * B / 100)