input parameter with three indices in LINGO software

Question

i want to input parameter with three indices in LINGO software but i don't know how to input this parameter in sets. for example in following sets i want to input D parameter with p,m and t indices. can anyone help me how to define parameter D?

model:
calc:
p=4;
m=2;
t=4;
endcalc

sets:
prod/1..p/;
mark/1..m/;
per/1..t/;