'''
for i in [1, 2, 3]:
    print(i)

for i in "abcd":
    print(i)

for i in range(5): #0~4
    print(i)

for i in range(1, 6): #1~5
    print(i)

for i in range(1, 6, 1): #1~5 1씩 커지게
    print(i)

for i in range(1, 6, 2): #1~5 2씩 커짐
    print(i)

for i in range(10, 1, -2):
    print(i)
'''

s = 0
for i in range(1, 11, 1):
    s = s + i

print(s)