794 B | 754 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
BLANK = " "
#inp = input
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
while 1:
N, M, K = mii()
# N: 첫번째 행의 침 수
# M: 전체 행 수
# K: 반복되는 패턴의 행수???
if N == M == K == 0:
break
k = mii()
crt = N
s = N
for idx in range(M - 1):
i = idx % K
crt += k[i]
s += crt
p(s)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()