How to get a differential gain > 40V/V?

How to get a differential gain > 40V/V with a diferential pair with PMOS input stage and resistive loads with Vdd=2.5V, Vss=-2.5V and Vo=0V by changing any value of bias current, transistor size and resistance?

Differential Amplifier with Resistive Loads

* Set options

.option post probe

* Element Statements

vdd vdd 0 2.5

vss vss 0 -2.5

m1 vout- vin+ 1 vss cmosn w=100u l=1.0u

m2 vout+ vin- 1 vss cmosn w=100u l=1.0u

r1 vdd vout- 50k

r2 vdd vout+ 50k

i1 1 vss 100u

e1 vin+ 2 3 vss 0.5

e2 vin- 2 3 vss -0.5

vcm 2 vss 2.5

vs 3 vss dc=0

* Control statements

.dc vs -0.5 0.5 0.01

.probe v(vout+,vout-)

.tf v(vout+,vout-) vs

.op

* Include device model with filename "cmos05.mod"

.include cmos05.mod

.end