#include <stdio.h>
#include <ctype.h>
#define NMAX 800

unsigned short v[NMAX];

FILE *fin;
unsigned short readshort(){
    unsigned short rez;
    char ch;
    while (!isdigit(ch = fgetc(fin)));
    rez = 0;
    while (isdigit(ch)){
        rez = rez * 10 + ch - '0';
        ch = fgetc(fin);
    }
    return rez;
}

int main(){
    FILE *fout;
    int n, i, j, k, cnt;

    fin = fopen ("nrtri.in", "r");
    n = readshort();
    for (i = 0; i < n; i++)
        v[i] = readshort();
    fclose (fin);

    cnt = 0;
    for (i = 0; i < n - 2; i++)
        for (j = i + 1; j < n - 1; j++)
            for (k = j + 1; k < n; k++)
                if (v[i] <= v[j] + v[k] && v[j] <= v[i] + v[k] && v[k] <= v[i] + v[j])
                    cnt++;

    fout = fopen ("nrtri.out", "w");
    fprintf (fout, "%d\n", cnt);
    fclose (fout);

    return 0;
}