Transforming columns in SPSS/R

#1
Hi!
In a research project I am doing, participants are asked to compare two texts and select which text they find easier to read. Each participant will be asked to do this ten times. There are 25 texts, from which a random subset of two texts will be presented each time.
When downloading the data from Qualtrics, it is presented as a long row per participant, showing which texts are shown and which text is the 'winner' of both. However, to perform a Bradley-Terry analysis, the data should be converted to a format in which each row represents one comparison.
In the image below, I tried to visualize this. Only in the image there are only three texts, the actual output will be with 25 texts and 10 comparisons per participant.
17092018.PNG

Could you help me with how I can easily transform my data to this format? Thanks!