1.2 KB | 1197 chars
"""
[27970: OX](https://www.acmicpc.net/problem/27970)
Tier: Silver 1
Category: ad_hoc, math
"""
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
SYS_INPUT = True
RECURSION_LIMIT = 10 ** 7
SET_RECURSION = True
BLANK = " "
if SET_RECURSION:
sys.setrecursionlimit(RECURSION_LIMIT)
inp = lambda : sys.stdin.readline().rstrip() if SYS_INPUT else input()
mii = lambda : [*map(int,inp().split())]
mfi = lambda : [*map(float,inp().split())]
ii = lambda : int(inp())
fi = lambda : float(inp())
isplit = lambda : inp().split()
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)
s = ""
n = 0
d = [1, 2]
MOD = 1000000007
def f(s, last_idx):
while last_idx >= 0:
if s[last_idx] == "O":
break
last_idx -= 1
if(last_idx < 0):
return 0
if last_idx == 0:
return 1
k = d[last_idx]
return (k + f(s, last_idx - 1)) % MOD
def solve():
global s, n, d
for i in range(2, 100001):
d.append((d[-1] * 2) % MOD)
s = inp()
n = len(s)
ret = f(s, n - 1)
p(ret)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()