My solution is accepted on CodeChef

import fileinput
def votersList():
   IDCounter = {};
   for line in fileinput.input():
     if not(fileinput.isfirstline()):       
       key = int(line)
       IDCounter[key] = IDCounter.get(key,0) + 1
   IDCounter = [str(id) for id,count in sorted(IDCounter.items()) if count > 1]
   return IDCounter;
 
IDCounter = votersList()
print(str(len(IDCounter))+"\n"+"\n".join(IDCounter),end='')

def leadGame(scores):
   scores.append({'S':0,'T':0})
   best = {'W':0,'L':0}
   for index,score in enumerate(scores):
     previous = scores[index-1]
     scores[index] = {'S':score['S']+previous['S'], 'T':score['T']+previous['T']}
     lead = scores[index]['S'] - scores[index]['T']
     if abs(lead) > best['L']:
       best = {'W': 1 if lead>0 else 2,'L':abs(lead)}
   return best