"""
N
1 + 2 + 3 + 4 + ... + N
"""

n = int(input())

sum = 0
i = 1

while i <= n:
    sum += i
    i += 1

print(sum)

"""
n = 0
sum = 0
i = 1

0
"""

78a100d149569e06f47b37618906277a0ba6ec4d
<mask token>

<mask token>
while i <= n:
    sum += i
    i += 1
print(sum)
<mask token>

<mask token>
n = int(input())
sum = 0
i = 1
while i <= n:
    sum += i
    i += 1
print(sum)
<mask token>

"""
N
1 + 2 + 3 + 4 + ... + N
"""

n = int(input())

sum = 0
i = 1

while i <= n:
    sum += i
    i += 1

print(sum)

"""
n = 0
sum = 0
i = 1

0
"""
