Problems with which we often deals in programming requires us to approximate number of iterations that we are going to perform in loops.

Given below is a simple pseudo code for which you need to tell the number of iteration performed in the given nested list :

for ( int x1 = 1 ; x1 <= n ; x1++ )
   for ( int x2 = x1 ; x2 <= n ; x2++ ) 
      for ( int x3 = x2 ; x3 <= n ; x3++ )
    ……
       ……
          ……
        for ( int xm = x(m-1) ; xm <= n ; xm++ )
            it++ ;

Take initial value of $it$ as $0$ and value of $m$ and $n$ to be $25$ and $26$ respectively.