fn getline() -> String{
	let mut __ret=String::new();
	std::io::stdin().read_line(&mut __ret).ok();
	return __ret;
}

fn nfactorial(x: i64, y: i64) -> i64 {
    match y {
        0 => 1,
        _ => x * nfactorial(x-1, y-1) % 1000000007
    }
}

fn mpow( x: i64,  y: i64) -> i64 {
    let (mut r,mut xx,mut yy) = (1, x, y);
    
    while yy > 0 {
        if (yy % 2) == 1 {
            r = (r * xx) % 1000000007;
        }
        yy /= 2;
        xx = (xx * xx) % 1000000007;
    }
    
    return r;
}

fn main(){
	let s=getline();
	let a:Vec<_>=s.trim().split(' ').collect();
	let (n, m): (i64, i64) = (a[0].parse().unwrap(), a[1].parse().unwrap());
	let mut r = mpow(m, n);
	let mut zeros = m;
	let mut zdiv =1;
	(1..m).for_each(|i| {
	    let patterns = mpow(m-i, n) % 1000000007;
	    
	    r = (if (i % 2) == 0 {r + patterns * (zeros * mpow(zdiv, 1000000007-2) % 1000000007) % 1000000007} else {(r + 1000000007 - patterns * (zeros * mpow(zdiv, 1000000007-2) % 1000000007) % 1000000007) % 1000000007}) % 1000000007;
	    zeros = zeros * (m-i) % 1000000007;
	    zdiv = zdiv * (i+1) % 1000000007;
	});
	print!("{} ", r);
}