```go
package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	var n, v int
	fmt.Fscan(in, &n, &v)

	if v >= n-1 {
		fmt.Print(n - 1)
		return
	}

	cost := v
	fuel := v
	for city := 2; city <= n-1; city++ {
		fuel--
		remainingDist := n - city
		if remainingDist > v {
			target := remainingDist
			if fuel < target {
				buy := target - fuel
				cost += buy * city
				fuel += buy
			}
		}
	}
	fmt.Print(cost)
}
```