#include<stdio.h>

int v[801];
int main()
{
    freopen( "nrtri.in", "r", stdin );
    freopen( "nrtri.out", "w", stdout );
    int n, i, j, k, nrtri=0;
    scanf( "%d", &n );
     for( i=1; i<=n; i++ )
         scanf( "%d", &v[i] );
     for( i=1; i<=n-2; i++ )
        for( j=i+1; j<=n-1; j++ )
           for( k=j+1; k<=n; k++ )
              if( v[i]+v[j]>=v[k] && v[i]+v[k]>=v[j] && v[j]+v[k]>=v[i] )
                   nrtri++;
    printf( "%d", nrtri );
    return 0;
}