#include <cstdio>
int v[800];
int main(){
freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);
int t,nr=0,aux,i,j,x,n,schimbare;
scanf("%d",&n);
for(i=0;i<n;++i)
scanf("%d",&v[i]);

do{schimbare=0;
for(i=0;i<n-1;++i)
    if(v[i]>v[i+1]){
aux=v[i];
v[i]=v[i+1];
v[i+1]=aux;
schimbare=1;
}
}while(schimbare);

for(i=0;i<n-2;++i)
    for(j=i+1;j<n-1;++j)
        for(x=j+1;x<n;++x)
    if(v[x]<=v[i]+v[j]) nr++;
        else break;

printf("%d",nr);

return 0;
}