2023-03-12

# data = []
#
# for i in range(10):
#     v = input().split()
#     for j in range(len(v)):
#         v[j] = int(v[j])
#     data.append(v)
#
# x = 1
# y = 1
# data[x][y] = 9
#
# while True:
#     # print(x, y)
#     if data[x][y+1] == 0:
#         data[x][y+1] = 9
#         y = y+1
#     elif data[x][y+1] == 1:
#         if data[x+1][y] == 1:
#             break
#         elif data[x+1][y] == 2:
#             data[x + 1][y] = 9
#             break
#         elif data[x+1][y] == 0:
#             data[x+1][y] = 9
#             x = x+1
#     elif data[x][y+1] == 2:
#         data[x][y+1] = 9
#         break
#
# for i in range(10):
#     for j in range(10):
#         print(data[i][j], end=' ')
#     print()
#
#
#
# n=int(input())
# data = []
#
# for i in range(n):
#     v = [0] * n
#     data.append(v)
# data[0][0]=1
# cnt=1
# num=n*2-1
# c=int(n)
# a=0
# b=n-1
# for i in range(n):
#     data[0][i]=i+1
# for i in range(n*2):
#     if cnt%4==0:
#         for i in range(num//2):
#             b=b+1
#             c=c+1
#             data[a][b]=c
#         num=num-1
#         if num==1:
#             break
#         cnt=cnt+1
#     elif cnt%4==1:
#         for i in range(num//2):
#             a=a+1
#             c=c+1
#             data[a][b]=c
#         num=num-1
#         if num==1:
#             break
#         cnt=cnt+1
#     elif cnt%4==2:
#         for i in range(num//2):
#             b=b-1
#             c=c+1
#             data[a][b]=c
#         num=num-1
#         if num==1:
#             break
#         cnt=cnt+1
#     elif cnt%4==3:
#         for i in range(num//2):
#             a=a-1
#             c=c+1
#             data[a][b]=c
#         num=num-1
#         if num==1:
#             break
#         cnt=cnt+1
#
#
# for i in range(n):
#     for j in range(n):
#         print(data[i][j], end=' ')
#     print()

# n = int(input())
# data = []
# for i in range(n+2):
#     v = [0] * (n+2)
#     data.append(v)
#
# for i in range(n+2):
#     for j in range(n+2):
#         if i == 0 or j == 0 or i == n+1 or j == n+1:
#             data[i][j] = 9
#             # boundary
# '''
# [
#     [1, 2, 3],
#     [4, 5, 6],
#     [7, 8, 9],
#     [
#         [1, 2, 3],
#         [4, 5, 6],
# '''
# direct = [[0, 1],
#           [1, 0],
#           [0, -1],
#           [-1, 0]]
# drt = 0
#
# x = 1
# y = 1
# k = 1
# data[x][y] = k
# k += 1
#
# while True:
#     dx = direct[drt][0]
#     dy = direct[drt][1]
#
#     if data[x+dx][y+dy] == 0:
#         x += dx
#         y += dy
#         data[x][y] = k
#         k += 1
#     else:
#         drt += 1
#         drt %= 4
#     if (k-1) == n*n:
#         break
#
# for i in range(1, n+1):
#     for j in range(1, n+1):
#         print(data[i][j], end=' ')
#     print()

# def candy():
#     print('This is function area')
#
# def sumation(a, b):
#     return a + b
#
# print(sumation(10, 20))
# print(sumation(10.5, 22.3))
# print(sumation('Hello', 'World'))
#
# def var(a, b):
#     return a, b, a+b
#
# x, y, z = var(10, 20)
# print(x, y, z)

'''
[]: list
(): tuple
{}: dictionary
'''



# def sum(b):
#     c = 0
#     while b != 0:
#         c = c + b % 10
#         b = b // 10
#     return c
#
#
# def sum1(a):
#     while a//10!=0:
#         a=sum(a)
#     return a
#
#
#
# a=int(input())
# b=a
# c=0
#
# print(sum1(sum(a)))

def v(x):
    s = 0
    while True:
        s += (x % 10)
        x //= 10
        if x == 0:
            return s

n = int(input())

while n>=10:
    n = v(n)

print(n)