#include<cstdio>
#include<algorithm>
using namespace std;
int n,i,j,k,p,ct=0,v[810];

int cautbin(int val)
{
    int start = 0, step = (1<<23);
    for(;step ; step>>=1)
    {
        int index = start + step;
        if(index > n) continue;
        if(v[index] > val) continue;
        start = index;
    }
    return start;
}

int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++) scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    //for(i=1;i<=n;i++) printf("%d ", v[i]); printf("\n");
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
    {
        k=v[i]+v[j];
        //printf("k = %d\n", k);
        p=cautbin(k);
        //printf("i = %d j = %d %d\n", i, j, p);
        if(p == j) continue;
        //printf("%d\n", p-j);
        ct+=p-j;
    }
    //printf("%d\n", cautbin(5));
    printf("%d",ct);
}