At confidence, how large a sample should be taken to obtain a margin of error of for the estimation of a population proportion

At confidence, how large a sample should be taken to obtain a margin of error of for the estimation of a population proportion? assume that past data are not available for developing a planning value for . round up to the next whole number.

n=p.(p-1).(\frac{z_\alpha /2}{E})^2

you can calculate the required size using the above formula