CODE EXAMPLE FOR PYTHON

first duplicate

def Solution(a):
  arr = []
  value=[]
  for i in range(len(a)):
    if a[i] not in hash:
      hash.append(a[i])
    else:
      value.append(i)
  if len(value) ==0:
    return -1
  else:
    idx = min(value)
    return a[idx]

# a = [1,2,3,4,4,2]
a=[1,2,3,4]
Solution(a)