#include<stdio.h>
#define max 800
int main()
{freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);
    long long n,k,i,v[max],j,nr=0;
    scanf("%lld",&n);
    for(i=1;i<=n;i++) scanf("%lld",&v[i]);
    for(i=1;i<=n;i++)
    for(j=i+1;j<n;j++)
    for(k=i+j;k<=n;k++)
    if(v[i]+v[j]>=v[k]) nr++;
    printf("%lld",nr);
    return 0;
}