use std::io::*;
use std::str::FromStr;
use utils::*;

pub fn main() {
    let i = stdin();
    let mut o = Vec::new();
    run(i.lock(), &mut o);
    stdout().write_all(&o).unwrap();
}

fn run<R: BufRead, W: Write>(i: R, o: &mut W) {
    let mut i = CpReader::new(i);
    let (_n, q) = i.read2::<usize, usize>();
    let s: Vec<_> = i.read_line().as_bytes().iter().cloned().collect();
    let mut td = Vec::new();

    for _ in 0..q {
        let mut tdi = i.read_line().split(' ');
        let t = tdi.next().unwrap().as_bytes()[0];
        let d = tdi.next().unwrap().as_bytes()[0];
        let d = if d == b'L' { Dir::L } else { Dir::R };
        td.push((t, d));
    }
    let ans = solve(&s, &td);
    writeln!(o, "{}", ans).unwrap();
}
#[derive(Eq, PartialEq, Clone, Copy)]
enum Dir {
    L,
    R,
}
fn solve(s: &[u8], td: &[(u8, Dir)]) -> usize {
    let mut l = 0;
    let mut r = 0;
    for &(t, d) in td.iter().rev() {
        match d {
            Dir::L => {
                if s[l] == t {
                    l += 1;
                }
            }
            Dir::R => {
                if s[s.len() - r - 1] == t {
                    r += 1;
                }
            }
        }
        if l + r == s.len() {
            break;
        }
    }
    s.len() - (l + r)
}

mod utils {
    use super::*;

    pub struct CpReader<R: BufRead> {
        r: R,
        s: String,
    }

    macro_rules! fn_read {
        { $f:ident($($t:ident),*) } => {
            #[allow(dead_code)]
            pub fn $f<$($t: FromStr),*>(&mut self) -> ($($t),*) {
                let i = &mut self.read_line().split(' ');
                ($(read_next::<$t,_>(i)),*)
            }
        };
    }

    impl<R: BufRead> CpReader<R> {
        pub fn new(r: R) -> Self {
            CpReader {
                r: r,
                s: String::new(),
            }
        }
        pub fn read_line(&mut self) -> &str {
            self.s.clear();
            self.r.read_line(&mut self.s).unwrap();
            self.s.trim()
        }

        fn_read! { read2(T1, T2) }
        fn_read! { read3(T1, T2, T3) }
        fn_read! { read4(T1, T2, T3, T4) }
        fn_read! { read5(T1, T2, T3, T4, T5) }
    }
    fn read_next<'a, T: FromStr, I: Iterator<Item = &'a str>>(i: &mut I) -> T {
        i.next().unwrap().parse().ok().unwrap()
    }

}
