fn main() {
    let mut temp = String::new();
    std::io::stdin().read_line(&mut temp).ok();
    let temp: Vec<usize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let a = temp[0];
    let b = temp[1];
    let s = temp[2];

    let mut result = 0usize;
    for i in 1..=a.min(s) {
        let limit = (s / i).min(b);
        for j in 1..=limit {
            result += (a - i + 1) * (b - j + 1);
        }
    }
    println!("{}", result);
}