Helper function that multiplies 2 matrices F and M of size 2 * 2 , and puts the multiplication result back to F [ ] [ ]
function multiply ( F , M , m ) { let x = ( ( F [ 0 ] [ 0 ] * M [ 0 ] [ 0 ] ) % m + ( F [ 0 ] [ 1 ] * M [ 1 ] [ 0 ] ) % m ) % m ; let y = ( ( F [ 0 ] [ 0 ] * M [ 0 ] [ 1 ] ) % m + ( F [ 0 ] [ 1 ] * M [ 1 ] [ 1 ] ) % m ) % m ; let z = ( ( F [ 1 ] [ 0 ] * M [ 0 ] [ 0 ] ) % m + ( F [ 1 ] [ 1 ] * M [ 1 ] [ 0 ] ) % m ) % m ; let w = ( ( F [ 1 ] [ 0 ] * M [ 0 ] [ 1 ] ) % m + ( F [ 1 ] [ 1 ] * M [ 1 ] [ 1 ] ) % m ) % m ; F [ 0 ] [ 0 ] = x ; F [ 0 ] [ 1 ] = y ; F [ 1 ] [ 0 ] = z ; F [ 1 ] [ 1 ] = w ; }