The Winged Dragon of Ra

As an additional cost to cast this spell, sacrifice three non-token creatures. This spell can't be countered.
Shroud.
• The Winged Dragon of Ra enters the battlefield with X +1/+1 counters, where X is equal to the total toughness of the creatures sacrificed to cast it.
• Pay X life points: make The Winged Dragon of Ra gain
X +1/+1 counters.
• Remove X +1/+1 counters from The Winged Dragon of
Ra: gain X life.
If The Winged Dragon of Ra is cast or put onto the battlefield without paying it'