Build failed, illegal characers in path.

I'm new to unity and i'm facing a problem. In the tutorial "Roll A Ball" game when i build the C# code it shows Build failed, illegal characters in path. I tried so much to remove it but problem isn't resolved.Due to t$$anonymous$$s ,i'm unable to do anyt$$anonymous$$ng further in unity. When i $$anonymous$$t play and give input not$$anonymous$$ng happens. So please help me over t$$anonymous$$s issue. Thanks in advance.