here is a simple case ,but cvx says i cant use a variable as denominater.i think i violate the DCP ruleset, but i dont know how to fix it, can anybody help me

cvx_begin
variables a
minimize(log(1+1/a)*a)
subject to
1<=a<=5
cvx_end

the errors are :
Disciplined convex programming error:
Cannot perform the operation: {positive constant} ./ {real affine}