import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Solution to Triangular Collection
 * 
 * @author vanb
 */
public class triangular_n3_vanb
{
    /** Input. */
    private static Scanner sc;
    
    /** Output. */
    private static PrintStream ps;
    
    /**
     * Do it!
     */
    private void doit()
    {
        int n = sc.nextInt();
        
        // Powers of 2 will be useful
        long power2[] = new long[n+1];
        power2[0] = 1L;
        for( int i=1; i<=n; i++) power2[i] = power2[i-1]*2L;
        
        // Read the numbers, sort them (smallest first).
        int a[] = new int[n];
        for( int i=0; i<n; i++ ) a[i] = sc.nextInt();
        Arrays.sort( a );
        
        // Go through all pairs, find all sets with each pair as the smallest two values.
        long total = 0;
        for( int i=0; i<n; i++ ) for( int j=i+1; j<n; j++ ) 
        {
            // Three values x, y and z can form a triangle iff x+y>z, x+z>y and y+z>x.
            // Starting with the smallest values for x and y, find all values of z where x+y>z
            // We know that x<y<z. So if x+y>z, then z+y>x+y>z>x, so z+y>x.
            // You can also show by the same logic that z+x>y. So, all we have to do is find the 
            // values in the array which are greater than a[j] (later in the list since it's sorted), 
            // but less than a[i]+a[j].
            int target = a[i] + a[j];
            int k;
            for( k=j+1; k<n && a[k]<target; k++ );
            
            // OK, a[k] is the first value >=a[i]+a[j] (or k==n).
            // So, there are k-j-1 values in the list which are greater than a[j] but smaller than a[i]+a[j].
            // Any combination of them can form a triangular set with a[i] and a[j], except the empty set.
            // Thus, there are (k-j-1)^2 - 1 sets found here.            
            total += power2[k-j-1]-1L;
        }
        
        ps.println( total );
    }
        
    /**
     * Main.
     * 
     * @param args unused
     * @throws Exception
     */
    public static void main( String[] args ) throws Exception
    {
        sc = new Scanner( System.in );
        ps = System.out;
        
        new triangular_n3_vanb().doit();
    }

}