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#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

long arr[2002];

int binarySearch(int start, int end, int x){

while(end > start){

int mid = (start + end) / 2;
if(arr[mid] > x){
end = mid;
}
else{
start = mid + 1;
}
}

return end;
}

int main(){

int n, b;
long result = 0;
while(true){
cin >> n;
if(n == 0)
break;

for(int i = 0; i < n; i++){
cin >> arr[i];
}

sort(arr, arr + n);

result = 0;
for(int i = 0; i < n; i++){
for(int j = i + 1; j < n; j++){

if(arr[i] + arr[j] < arr[n - 1]){

  /* Find the first element which is greater than sum of two element */
b = binarySearch(i, n - 1, arr[i] + arr[j]);
result += (n - b);
}
}
}

cout << result << endl;
}
return 0;
}