n=int(input())

string=input().split()

count={}

ss=[]

for i in string:

    if i in count:

        count[i] +=1

    else:

        count[i] = 1

for i in string:

  if i not in ss:

      ss.append(i)

      



dem= len(ss)

print(dem)

a=sorted(ss)

for i in sorted(count, key=count.get, reverse=False): 

  print(i, count[i])
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