Power function to calculate long powers with mod
function power ( x , y , p ) { let res = 1 ; x = x % p ; if ( x == 0 ) return 0 ; while ( y > 0 ) { if ( ( y & 1 ) != 0 ) res = ( res * x ) % p ; y = y >> 1 ; x = ( x * x ) % p ; } return res ; }