package main

import . "fmt"

func main() {
	var a,b,s int
	Scan(&a,&b,&s)
	ans := 0
	for r := 1; r <= min(b, s); r++ {
		maxc := min(a, s / r)
		tmp := (a + 1) * maxc - maxc * (maxc + 1) / 2
		ans += (b - r + 1) * tmp
	}
	Println(ans)
}