#include "testlib.h"
#include <bits/stdc++.h>

using namespace std;

int main(int argc, char* argv[]){
  registerValidation(argc, argv);

  long long n=inf.readLong(2ll,200000ll);inf.readEoln();
  vector<long long> a=inf.readLongs(n,1ll,1000000000ll);inf.readEoln();
  inf.readEof();
  a.push_back(-1);
  long long curl=1,res=0;
  for(long long i=1;i<=n;i++){
    if(a[i-1]+1 == a[i]){curl++;}
    else{
      res+=(curl*(curl-1))/2;
      curl=1;
    }
  }
  cout << res << "\n";
  return 0;
}