i^2=- 1

i^3=i*i^2=-i

i^4=(- 1)^2= 1

i^5=i^4*i=i

i^6=i^2=- 1

i^7=i^3=-i

……

Every four results will cycle, that is, four cycles.

The remainder of 20 10/4=502 is 2, and I+I 2+I 3+I 4 = I-1-I+1= 0, so

1+i+i's square +i's cube +i's fourth power +i's 20 10 power.

= 1+0+i- 1

= me