A Triangular Slice of Squared Pi Inspired by Bake a slice of Pi

Challenge

Given input 3 &lt;= n &lt;= 100 and 3 &lt;= y &lt;= n, construct an n x n matrix of the decimal portion of pi (14159...), starting in the top left. Then, take the upper-right triangle of size y x y and concatenate it together. Output the resulting number.

For example, for input n = 5, y = 3, the following matrix is constructed

14159
26535
89793
23846
26433


Then, the upper-right 3 x 3 triangle would be

159
 35
  3


so 159353 is the output.

Input

Two integers -- n representing the size of the square matrix of the digits of pi, and y representing the upper-right triangle -- in any convenient format.

Output


The resulting sliced and concatenated number, either printed/displayed to the screen, returned as a string, etc.
Trailing/leading whitespace is optional, so long as there's no whitespace in the output (i.e., 159 35  3 or the like would be invalid).
Note that since we're explicitly looking for the digits of pi, and not an approximation or mathematical calculation, answers should not round the final digit of the matrix.


Rules


This is code-golf so all the usual rules for golfing apply, and the shortest code (in bytes) wins.
Either a full program or function are acceptable.
Standard loopholes are forbidden.


Examples

 n  y  output
-------------
 3  3  141923
 5  3  159353
 6  4  1592589383
 6  6  141592535893238643794
20 12  358979323846950288419715820974944628620899211706792306647223172745025559196615
05AB1E, 19 bytes

Uses CP-1252 encoding.

nžs¦¦¹ôI£íRvyN&gt;£J}R


Try it online!

Explanation

n=5, y=3 used for example

nžs                  # push pi to n^2 digits
                     # STACK: 3.1415926535897932384626433
   ¦¦                # remove the first 2 chars
                     # STACK: 1415926535897932384626433
     ¹ô              # split into n*n matrix
                     # STACK: ['14159', '26535', '89793', '23846', '26433']
       I£            # keep the first y rows
                     # STACK: ['14159', '26535', '89793']
         íR          # reverse the list of rows and each individual row
                     # STACK: ['39798', '53562', '95141']
           v     }   # for each y,N (row, index) in the list
            yN&gt;£J    # keep the first index+1 digits of the row and join to string
                     # STACK: 353951
                  R  # reverse the string
                     # STACK: 159353
                     # implicit print