l:.'(0:"i/1")
*/1|,/l*2020=l+/:l
*/?1|,//l*2020=l+\:l+/:l

/ first version:
/*1_?,/{{x*y*2020=x+y}[x]'l}'l
/*1_?,/,/{{{x*y*z*2020=x+y+z}[x;y]'l}[x]'l}'l