m, n = 20, 20
num = 1
x, y = 0, 0
cnt = m + n - 1
a = [[0] * (2 * n + 1) for _ in range(2 * m + 1)]
dir = [(-1, 1), (1, -1)]
for i in range(cnt):
    for j in range(i + 1):
        a[x][y] = num
        num += 1
        x += dir[i % 2][0]
        y += dir[i % 2][1]
    if i % 2 == 0:
        x = 0
    else:
        y = 0

# print(*a, sep='\n')
print(a[19][19])