Queen's Gambit Declined Slav accepted - Alapin variation
1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 dxc4 5. a4
White advances the queen's pawn to d4. Black plays the queen's pawn to d5. White advances the c-pawn to c4.
Black plays the c-pawn to c6. White develops the knight to f3. Black develops the knight to f6.
White moves the knight to c3. Black captures on c4 with the queen's pawn. White advances the a-pawn to a4.