import java.util.Scanner;
class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int now = sc.nextInt();
        int count = 1;
        int ans = 0;
        while(--N>0){
            int next = sc.nextInt();
            if(++now==next)
                ++count;
            else{
                now = next;
                ans += count*(count-1)/2;
                count = 1;
            }
        }
        System.out.println(ans+count*(count-1)/2);
    }
}