#include <fstream>
#include <cstdio>
#include <algorithm>
using namespace std;
int n,i,v[810],j,k,tri;
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)
        for(j=i+1;j<=n;++j)
            for(k=j+1;k<=n;++k)
                if(v[i]+v[j]>=v[k])
                    ++tri;
                else
                    break;
    printf("%d",tri);
    return 0;
    }