func sol() -> Int {
    guard let input = readLine() else { return 0 }
    let info = input.split(separator: " ").compactMap{Int($0)}
    
    let ans = { (a: Int, b: Int) -> Int in return a - b > 0 ? a - b : 0 }
    
    return ans(info[0]*info[1], info[2])
}

print(sol())