C90

Use rpsrunner.py to play unranked matches on your computer.

Source code:

x = 558273                                                                      
                                                                                
def semilla(n): global x; x = n                                                 
                                                                                
def alea():                                                                     
    global x                                                                    
    x = x * 1103515245 + 12345                                                  
    return ((x >> 16) % 32768) % 3                                              
                                                                                
output = ['R', 'P', 'S'][alea()]