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}

出错 ./ (line 19)

z = times( x, y, ‘./’ );

出错 * (line 36)

z = feval( oper, x, y );

出错 / (line 15)

z = mtimes( x, y, ‘rdivide’ );

出错 Untitled2 (line 4)

minimize(log(1+1/a))*a