// Enter your code here 
var arr: [Double] = []
if let line = readLine() {
    for chr in line.characters {
        if chr != " " {
            arr.append(Double(String(chr)) ?? 0)
        }
    }
}

var sum = 0.5*arr[0]*arr[2] + 0.5*arr[1]*arr[2]
sum = sum % (10*10*10*10*10*10*10*10*10 + 7)
print(Int(sum))