#include <cstdio>
#include <algorithm>

using namespace std;

int n,v[820];

inline void Read()
{
    int i;
    FILE *f = fopen("nrtri.in","r");
    fscanf(f,"%d ",&n);
    for(i = 1; i<= n;++i)
        fscanf(f,"%d ", &v[i]);
    sort(v+1,v+n+1);
    fclose(f);
}

inline void Solve()
{
    int i,j,suma = 0,p,sol = 0;
    for( i = 1; i< n;++i)
        for( j = i+1 ; j<=n ;++j)
        {
            suma=v[i]+v[j];
            p = j+1;
            while( suma >= v[p] && p<=n )
            {
                p++;
                sol++;
            }

        }
    FILE *g = fopen("nrtri.out","w");
    fprintf(g,"%d ", sol);
}

int main()
{
    Read();
    Solve();
    return 0;
}