package main

import . "fmt"
import . "os"
import bf "bufio"

func main() {
	rd:=bf.NewReader(Stdin)
	var n int
	Fscan(rd,&n)
	ans, c, p := 0, 0, -1
	for i := 0; i < n; i++ {
		var a int
		Fscan(rd, &a)
		if a - p != 1 {
			if c >= 2 {
				ans += c*(c-1)/2
			}
			c = 0
		}
		c++
		p = a
	}
	if c >= 2 {
		ans += c*(c-1)/2
	}
	Println(ans)
}