#[allow(unused_imports)]
use std::cmp::{Ordering};

#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};

#[allow(unused_imports)]
use std::io::{stdin, stdout, BufWriter, Write};

#[allow(unused_imports)]
use std::iter::FromIterator;

#[allow(unused_macros)]
macro_rules! min {
    ($x: expr) => ($x);
    ($x: expr, $($z: expr),+) => {{
        std::cmp::min($x, min!($($z),*))
    }}
}

#[allow(unused_macros)]
macro_rules! max {
    ($x: expr) => ($x);
    ($x: expr, $($z: expr),+) => {{
        std::cmp::max($x, max!($($z),*))
    }}
}

#[allow(unused_macros)]
macro_rules! get { 
    ([$t: ty]) => { 
        { 
            let mut line = String::new(); 
            stdin().read_line(&mut line).unwrap(); 
            line.split_whitespace().map(|t|t.parse::<$t>().unwrap()).collect::<Vec<_>>()
        }
    };
    ([$t: ty];$n: expr) => {
        (0..$n).map(|_|get!([$t])).collect::<Vec<_>>()
    };
    ($t: ty) => {
        {
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            line.trim().parse::<$t>().unwrap()
        }
    };
    ($($t: ty),*) => {
        { 
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            let mut iter = line.split_whitespace();
            ($(iter.next().unwrap().parse::<$t>().unwrap(),)*)
        }
    };
    ($t: ty; $n: expr) => {
        (0..$n).map(|_|get!($t)).collect::<Vec<_>>()
    };
    ($($t: ty),*; $n: expr) => {
        (0..$n).map(|_|get!($($t),*)).collect::<Vec<_>>()
    };
}

#[allow(unused_macros)]
macro_rules! debug {
    ($($a:expr),*) => {
        #[cfg(debug_assertions)]
        writeln!(&mut std::io::stderr(), concat!("[DEBUG] ", $(stringify!($a), "={:?} "),*), $($a),*).unwrap();
    }
}

const BIG_STACK_SIZE: bool = true;

#[allow(dead_code)]
fn main() {
    use std::thread;
    if BIG_STACK_SIZE {
        thread::Builder::new()
            .stack_size(32 * 1024 * 1024)
            .name("solve".into())
            .spawn(solve)
            .unwrap()
            .join()
            .unwrap();
    } else {
        solve();
    }
}

//[lb, ub]でupper_boundを探す, [lb, ub]に存在しなかったらNone
fn upper_bound<F>(lb: usize, ub: usize, criterion: F) -> Option<usize>
    where 
        F: Fn(usize) -> bool 
{
    let mut lb = lb;
    let mut ub = ub+2;
    let umax = ub;
    while ub - lb > 1 {
        debug!(lb, ub);
        let mid = lb + (ub-lb)/2;
        if criterion(mid-1) {
            ub = mid;
        } else {
            lb = mid;
        }
    }
    debug!(lb, ub);
    if umax == ub {
        None
    } else {
        Some(ub)
    }
}
    

fn solve() {
    let (n, q) = get!(usize, usize);
    let s = get!(String).chars().collect::<Vec<_>>();
    let tdt = get!(String, String; q);
    let mut td = Vec::new();
    for (t, d) in tdt {
        td.push((t.into_bytes()[0] as char, d.into_bytes()[0] as char));
    }
    let mut count = 0;

    let right = |key| {
        let mut po = key;
        for &(t,d) in td.iter() {
            if s[po] == t {
                if d == 'L' {
                    if po == 0 {
                        break;
                    }
                    po -= 1;
                } else {
                    if po == n-1 {
                        return true;
                    }
                    po += 1;
                }
            }
        }
        false
    };

    let ub = upper_bound(0, n-1, right);
    debug!(ub);
    if let Some(v) = ub {
        count += n-v+1;
    }

    let left = |key| {
        let mut po = key;
        for &(t,d) in td.iter() {
            if s[n-po-1] == t {
                if d == 'L' {
                    if po == n-1 {
                        return true;
                    }
                    po += 1;
                } else {
                    if po == 0 {
                        return false;
                    }
                    po -= 1;
                }
            }
        }
        false
    };

    let ub = upper_bound(0, n-1, left);
    debug!(ub);
    if let Some(v) = ub {
        count += n-v+1;
    }

    println!("{}", n-count);
}


Measured memory_bytes: 24700