25_let_it_snow.py

###############################
# --- Day 25: Let It Snow --- #
###############################

import AOCUtils

###############################

rawInput = AOCUtils.loadInput(25).split()
row, col = int(rawInput[-3][:-1]), int(rawInput[-1][:-1])

start = 20151125
base = 252533
mod = 33554393

goal = (row+col-1) * (row+col) // 2 - row

n = (start * pow(base, goal, mod)) % mod

print("Part 1: {}".format(n))

AOCUtils.printTimeTaken()

'''
(2947, 3029)
2947+3029 = 5976

1,1 = 0

2,1 = 1
1,2 = 2 = 2

3,1 = 3
2,2 = 4
1,3 = 5 = 2 + 3

4,1 = 6
3,2 = 7
2,3 = 8
1,4 = 9 = 2 + 3 + 4

5975,1 = 
5974,2 = 
...
2948,3028 = 
2947,3029 = 2 + 3 + 4 + ... + 5975 - (2947 - 1) = 1 + 2 + ... + 5975 - 2947
2946,3030 = 
...
1,5975 = 2 + 3 + 4 + ... + 5975

= 1 + 2 + 3 + ... + (2947+3029-1) - 2947
= (2947+3029-1) * (2947+3029) // 2 - 2947
= 17850353
'''