use proconio::input;

fn f(n: i64, x: i64) -> i64 {
    if n == -1 {
        0
    } else {
        n / x + 1
    }
}

fn main(){
    input!{
        a: i64,
        b: i64,
        x: i64,
    };

    let result = f(b, x) - f(a - 1, x);

    println!("{}", result);
}