"""
P5721 【深基4.例6】数字直角三角形
https://www.luogu.com.cn/problem/P5721
"""
cnt=0
n=int(input())
for i in range(1,n+1):
for j in range(i,n+1):
cnt+=1
if cnt<10:
print("0",end='')
print(cnt,end='')
print()