1.1 KB | 1145 chars
"""
[33026: LOL Lovers](https://www.acmicpc.net/problem/33026)
Tier: Bronze 3
Category: implementation, string
"""
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 = False
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)
def solve():
n = ii()
s = inp()
l_cnt = s.count("L")
o_cnt = s.count("O")
crt_l = 0
crt_o = 0
for i in s[:-1]:
if i == "L":
crt_l += 1
elif i == "O":
crt_o += 1
left_l = l_cnt - crt_l
left_o = o_cnt - crt_o
if crt_l != left_l and crt_o != left_o:
return crt_l + crt_o
return -1
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()
p(ret)