Benko gambit - Zaitsev system
1. d4 Nf6 2. c4 c5 3. d5 b5 4. cxb5 a6 5. Nc3
White pushes the queen's pawn to d4. Black develops the knight to f6. White pushes the c-pawn to c4.
Black pushes the c-pawn to c5. White advances the queen's pawn to d5. Black plays the b-pawn to b5.
White captures on b5 with the c-pawn. Black advances the a-pawn to a6. White develops the knight to c3.