#include <cstdio>
#include <algorithm>
#define NMAX 5002
using namespace std;

int n,nr,poz;
int V[NMAX];

inline void citesc(){

    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(register int i=1;i<=n;++i)
        scanf("%d",&V[i]);
}

inline void solve(){

    sort(V+1,V+n+1);
    for(register int i=1;i<=n-2;++i){
        for(register int j =i+1;j<=n-1;++j)
            for(register int z =j+1;z<=n;++z)
        if(V[i]+V[j] >=V[z])
            ++nr;
            else break;
    }
printf("%d",nr);
}

int main(){

    citesc();
    solve();
return 0;
}