@acer, many thanks for your help. 

@Joe Riel , many thanks for your help. 

@Carl Love , many thanks for your help. It worked perfectly. 

@Rouben Rostamian  

Many thanks for your help. 

@Kitonum 

Many thanks for the quick response. 

Many thanks for the responses. I will follow your advices. 

I'm using Windows 10 64bit and Maple 18. 

@Mariusz Iwaniuk 

Many thanks!