Write a code to generate a half pyramid number pattern.

def pattern(n):
    for i in range(n):
        if i % 2 == 0:
            for j in range(n-i):
                print(j+1, end = "")
        else:
            for j in range(n-i, 0, -1):
                print(j, end = "")
        print()
n = int(input())
pattern(n)