// https://yukicoder.me/problems/no/1467
// これっぽい感が

fn run() {
    input! {
        n: usize,
        m: usize,
        k: i64,
        b: [i64; n],
        r: [i64; m],
    }
    let mut map = std::collections::BTreeMap::new();
    for &b in b.iter() {
        map.entry(b % k).or_insert(vec![vec![]; 2])[0].push(b / k);
    }
    for &r in r.iter() {
        map.entry(r % k).or_insert(vec![vec![]; 2])[1].push(r / k);
    }
    let mut sum = 0;
    let mut cnt = 0;
    let inf = std::i64::MAX / 10;
    for (_, mut p) in map {
        if p[0].len() < p[1].len() {
            p.swap(0, 1);
        }
        let mut a = vec![];
        a.extend(p[0].iter().map(|p| (*p, 0)));
        a.extend(p[1].iter().map(|p| (*p, 1)));
        a.sort();
        let mut left = std::collections::BinaryHeap::new();
        let mut add = 0;
        left.push((0, inf));
        if a[0].0 == 0 {
            add -= 1;
        } else {
            add += 1;
        }
        for a in a.windows(2) {
            let diff = a[1].0 - a[0].0;
            let mut d = diff;
            let op = a[1].1;
            while d > 0 && left.peek().map_or(false, |p| p.0 + add > 0) {
                let (a, b) = *left.peek().unwrap();
                let v = b.min(d);
                sum += (a + add) * v;
                d -= v;
                if b == v {
                    left.pop();
                } else {
                    left.peek_mut().unwrap().1 -= v;
                }
            }
            let d = 2 * diff - d;
            if d > 0 {
                left.push((-add, d));
            }
            if op == 0 {
                add -= 1;
            } else {
                add += 1;
            }
        }
        for v in left.drain() {
            let pos = v.0 + add;
            let cnt = v.1;
            sum += cnt * std::cmp::max(0, pos - 0);
        }
        cnt += p[1].len();
    }
    if cnt == n.min(m) {
        println!("{}", sum);
    } else {
        println!("-1");
    }
}

fn main() {
    run();
}

// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------