#include<bits/stdc++.h>
#define in f
#define out g
using namespace std;

ifstream f ("nrtri.in");
ofstream g ("nrtri.out");

int n;
int v[801];
int r;

int main() {

    for(int i = 1; i <= n; i++) {
        in >> v[i];
    }
    for(int i = 2; i <= n; i++) {
        for(int j = i + 1; j <=n; j++) {
            if(v[i]+v[i-1] >= v[j]) {
                r++;
            }
        }
    }
    out << r;

}