// Enter your code here 
let arr = readLine()!.characters.split(" ").map{Int(String($0))!}

func modulo(num: Int) -> Int {
    func power(num: Int, by: Int) -> Int {
        var power = 1
        for _ in 1...by {
            power *= num
        }
        
        return power
    }
    return num % (power(10, by: 9) + 7)
}

func calculateProbability(factorA a: Int, factorB b: Int, milliseconds time: Int) -> Int {
    let numOfVirusCells = Int((0.5 * Double(a) * Double(time)) + (0.5 * Double(b) * Double(time)))
    
    return modulo(numOfVirusCells)
}

print(calculateProbability(factorA: arr[0], factorB: arr[1], milliseconds: arr[2]))