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import sys
limit_number = 15000 파이썬 재귀 제한 해제
sys.setrecursionlimit(limit_number)
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x = input()
x = int(x)
def rec(x):
if x == 1:
return 1
else:
return x + rec(x-1)
print(rec(x))
x, y = input().split()
x = int(x)
y = int(y)
def rec(f, u):
if f == 0 or u == 0: #0 아닐때
return 0
elif f > u: # 같을때
return 0
else: # 홀수일때
if f % 2 != 0:
print(f, end=" ")
rec(f+1, u)
rec(x, y)
__________________________________________________________
# def pibo(x):
# if x <= 2:
# memo[x] = 1
# return memo[x]
#
# if memo[x] != 0:
# return memo[x]
#
# memo[x] = (pibo(x-1)%10009 + pibo(x-2)%10009)%10009
# return memo[x]
#
# n = int(input())
# print(pibo(n)%10009)
___________________________________________________________
memo = []
for i in range(51):
v = [1] * 51
memo.append(v)
x, y = input().split()
x = int(x) #가로
y = int(y) #세로
for i in range(100): #가로
for j in range(100):#세로
if i == x and j == y:
print(memo[i][y])
break
else:
memo[i][j] = memo[i-1][j] + memo[i][j+1]