identify the miRNA response elements (mres)

Question

[Sam]

Dear Biostars

I'm working on ceRNA network analysis, and I need to identify the miRNA response elements (mres) in the target genes of miRNAs

could you introduce me R library or web server for identification of mres? To have this data as output

Mirna         Target    energy   gap_l  gap_r
hsa-let-7b-5p   RB1 -17.27  2085    2104
hsa-let-7b-5p   RB1 -21.37  2482    2503
hsa-let-7b-5p   SOX5    -31.33  640 662
hsa-let-7b-5p   SOX5    -31.33  715 737

P.S this is one of input data for ceRNAseek library but in the manual no mentioned how they calculated this!