# Topic : Greedy _ 알바생 강호
#
# Python 3 : 3952ms
# PyPy 3 : 192ms

N = int(input())

tips = [ int(input()) for _ in range(N) ]

tips.sort(reverse=True)

result = 0
for i in range(N):
  tmp = tips[i] - i 
  if tmp < 0:
    tmp = 0
  result += tmp

print(result)