661 B | 641 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
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():
n, g, r = mii() # 녹색불 시간, 빨간불 시간
l = mii()
ans = 0
i = 0
while i < n:
left = g
while i < n and l[i] <= left:
ans += l[i]
left -= l[i]
i += 1
if i != n:
ans += left + r
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()