#include <stdio.h>
#include <stdlib.h>

int v[800];
int main()
{
    int n, i, nrtri, schimb, j, i2, i3;
    FILE *fin, *fout;
    fin=fopen("nrtri.in", "r");
    fout=fopen("nrtri.out", "w");
    fscanf(fin, "%d", &n);
    for(i=0; i<n; i++){
        fscanf(fin, "%d", &v[i]);
    }
    for(i=0; i<n-1; i++){
        for(j=i+1; j<n; j++){
            if(v[i]>v[j]){
                schimb=v[i];
                v[i]=v[j];
                v[j]=schimb;
            }
        }
    }
    for(i=0; i<n; i++){
    }
    nrtri=0;
    for(i=0; i<n-2; i++){
        for(i2=i+1; i2<n-1; i2++){
            i3=n-1;
            while(v[i3]>v[i]+v[i2] && i3>i2){
                i3--;
                nrtri++;
            }
        }
    }
    fprintf(fout, "%d", nrtri);
    return 0;
}