#include <cstdio>
#include <algorithm>
#define NMax 30001

using namespace std;

long n,vmin[NMax+NMax],vmax[NMax+NMax],v[NMax],minn,maxx,rez;

int bsearchMin(long in,long fn,long v[],long val) {
    long mid;
    if(v[fn]<=val)
        return fn;
    else
        if(val<v[1])
            return 0;

    while(in<=fn) {
        mid=(fn-in)/2+in;
        if(v[mid]<=val&&val<v[mid+1])
            return mid;
        else
            if(val<v[mid])
                fn=mid-1;
            else
                in=mid+1;
    }
    return 0;
}

int bsearchMax(long in,long fn,long v[],long val) {
    long mid;
    if(v[fn]<val)
        return 0;
    else
        if(val<=v[1])
            return 1;

    while(in<=fn) {
        mid=(fn-in)/2+in;
        if(v[mid]>=val&&val>v[mid-1])
            return mid;
        else
            if(val<v[mid])
                fn=mid-1;
            else
                in=mid+1;
    }
    return 0;
}

bool comp(long a,long b) {
    if(a<=b)
        return 1;
    return 0;
}

int main()
{
    freopen("nrtri.in","rt",stdin);
    freopen("nrtri.out","wt",stdout);
    scanf("%ld",&n);
    for(long i=1;i<=n;i++)
        scanf("%ld",&v[i]);

    sort(v+1,v+n+1,comp);

    for(long i=0;i<=NMax+NMax;i++) {
        vmin[i]=bsearchMin(1,n,v,i);
        vmax[i]=bsearchMax(1,n,v,i);
    }

    v[1]=v[1];
    for(long i=1;i<n;i++)
        for(long j=i+1;j<=n;j++) {
            minn=vmax[v[j]];
            maxx=vmin[v[j]+v[i]];
            if(v[j]<v[minn])
                minn--;
            if(v[i]==v[minn])
                minn++;
            rez+=maxx-minn>0 ? maxx-minn : 0;
        }

    printf("%ld\n",rez);

    return 0;
}