Estmating Allele Frquency and Snps number

Question

[brendaumoh6]

Hello all,I am working with a Gwas summary statistics data which was downloaded from GWAS catalog. It doesnt have all the columns needed for my analysis. However it lacks effect Allele Frequency and N (The SNP sample sizes) columns. Please how do I derive Freq and N from estimation for my analysis. However these are the following columns have: a1,a2,pval,beta,se and snpid (chr:pos)