*Inspired by [Bake a slice of Pi](https://codegolf.stackexchange.com/q/93615/42963)*

### Challenge

Given input `3 <= n <= 100` and `3 <= y <= 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](https://codegolf.meta.stackexchange.com/q/2447/42963).

### 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](/questions/tagged/code-golf "show questions tagged '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](https://codegolf.meta.stackexchange.com/q/1061/42963) are forbidden.

### Examples

```
 n  y  output
-------------
 3  3  141923
 5  3  159353
 6  4  1592589383
 6  6  141592535893238643794
20 12  358979323846950288419715820974944628620899211706792306647223172745025559196615

```