#include <bits/stdc++.h>
using namespace std;

int main(){
  int N, a, b, fr, ba, count;
  count = 0;
  cin >> N;
  vector<int> yu(N-1);
  cin >> a;
  for(int i =0; i < N-1; i++){
    cin >> b;
    yu[i] = b-a;
    a = b;
  }
  for(int i = 0;i<N-1; i++){
    fr= i;
    ba= i;
    while(fr >= 0 && ba < N-1){
      if(yu[fr] != yu[ba]){
        break;
      }
      count++;
      fr--;
      ba++;
    }
  }
  for(int i = 0;i<N-2; i++){
    fr= i;
    ba= i+1;
    while(fr >= 0 && ba < N-1){
      if(yu[fr] != yu[ba]){
        break;
      }
      count++;
      fr--;
      ba++;
    }
  }
  cout << count + N << endl;
}