Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Year | Title | System | Developer | Publisher |
| --- | --- | --- | --- | --- |
| 1984 | Ghostbusters | Atari 800, Commodore 64, MSX, ZX Spectrum, Amstrad CPC | Activision | Activision |
| 1985 | Ghostbusters | Atari 2600, Apple II | Activision | Activision |
| 1987 | The Real Ghostbusters | Arcade | Data East | Data East |
| 1987 | Ghostbusters | Sega Master System | Activision | Sega |
| 1988 | Ghostbusters | NES | Bits Laboratory | Activision/Tokuma Shoten |
| 1989 | The Real Ghostbusters | Commodore 64, Amiga, ZX Spectrum, Amstrad CPC, Atari ST | Data East | Activision |
| 1989 | Ghostbusters II | Atari 2600, Amiga, Commodore 64, MSX, PC, ZX Spectrum, Amstrad CPC | Activision | Activision |
| 1990 | Ghostbusters II | NES | Kemco | Activision |
| 1990 | Ghostbusters | Sega Mega Drive/Genesis | Sega | Sega |
| 1990 | New Ghostbusters 2 | Game Boy, NES | Hal Laboratory | Activision |
| 1993 | The Real Ghostbusters | Game Boy | Kemco | Activision |
| 2009 | Ghostbusters: The Video Game | PlayStation 3, PlayStation 2, PlayStation Portable, Xbox 360, Nintendo DS, Wii, PC | Terminal Reality, Red Fly Studios, Zen Studios | Atari,\nSony Computer Entertainment (Europe only, PS2 and PS3 versions) |
| 2011 | Ghostbusters: Sanctum of Slime | PlayStation Network, Xbox Live, PC | Behaviour Interactive | Atari |
| 2012 | Ghostbusters: Paranormal Blast | Android, iOS | XMG Studio |  |
| 2013 | Ghostbusters | iOS | Beeline Interactive | Capcom |
Question:
what is the total amount of games activision developed?
Answer:
4