Based on great book, “Roadside Picnic” by Strugatsky brothers (Game Stalker:SoC was based on it). My russian is really rusty but based on the book it probably reads as follows:  
“Friendship”  
“For everyone. For free”  
“And let nobody be left without enough of it”
 
SPOILERS:
 
It is paraphrase of original ending in which main hero after making some brutal sacrifices reaches golden sphere that supposedly grants wishes and has problem articulating his personal wish and in the end says the following thing (with happiness instead of friendship). It is unknown if the globe works or not.