#include <stdio.h>
#define MAXN 800
#define MAXLEN 30000

int lenb[MAXN] , vfl[MAXLEN + 1];
int main () {
    FILE *fin , *fout;
    int n , i , j , lb , nrtri;

    fin = fopen ( "nrtri.in" , "r" );
    fscanf ( fin , "%d" , &n );

    for ( i = 0 ; i < n ; i++ ) {
        fscanf ( fin , "%d" , &lb );
        vfl[lb]++;
    }
    fclose ( fin );

    n = 0;
    for ( i = 1 ; i <= MAXLEN ; i++ )
        for ( j = 0 ; j < vfl[i] ; j++ ) {
            lenb[n] = i;
            n++;
        }
    for ( i = 1 ; i <= MAXLEN ; i++ )
        vfl[i] = vfl[i] + vfl[i - 1];

    nrtri = 0;
    for ( i = 0 ; i < n ; i++ )
        for ( j = i + 1 ; j < n ; j++ )
            nrtri = nrtri + vfl[lenb[i] + lenb[j]] - vfl[lenb[j] - 1] - 1;

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

    return 0;
}