I can not upload a FORTINET-FORTIGATE-MIB.mib at MIB Browser on opmanger

I can not upload a FORTINET-FORTIGATE-MIB.mib at MIB Browser on opmanger

I have fortigate 1000d firewalls and I want to moritor CPU and Memory. then I downloaded a Mib file on my firewall box 
and I got FORTINET-FORTIGATE-MIB file. It has size 235KB. then I used the opmanager browser to upload and I have got some error "MIB file upload failed"
then I go to drop down list at MIB Browser. I found the FORTINET-FORTIGATE.mib but I got the error "Error parsing MIB:FORTINET-FORTIGATE-MIB.mib.  
Exception while loading MIB:IMPORTS failed: Could not find the file : C:/ManageEngine/OpManager/bin/../mibs/HCNUM-TC
Please upload the above dependency MIB to load FORTINET-FORTIGATE-MIB.mib"

please help me.