#include<cstdio>
#include<algorithm>

using namespace std;

int v[810];

int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    int k=0,n;
    scanf("%d",&n);
    for(int a=1;a<=n;a++) scanf("%d",&v[a]);
    sort(v+1,v+n+1);
    for(int a=0;a<n-2;a++)
        for(int b=i+1;b<n-1;b++)
            for(int c=j+1;c<n;c++)
                if(v[a]+v[b]>=v[c]) k++;
                else break;
    printf("%d",k);
    return 0;
}