const MAX_T: usize = 100;
const MAX_N: usize = 200_000;
const MAX_M: usize = 200_000;
const MAX_K: i64 = 1_000_000_000;
const MAX_Y: i64 = 1_000_000_000;

fn read() -> Vec<(usize, i64, Vec<(usize, i64)>)> {
    let mut s = String::new();
    use std::io::Read;
    std::io::stdin().read_to_string(&mut s).unwrap();
    let mut it = s.trim().split_whitespace();
    let mut next = || it.next().unwrap().parse::<i64>().unwrap();
    let t = next() as usize;
    assert!(1 <= t && t <= MAX_T);
    let mut test = vec![];
    for _ in 0..t {
        let n = next() as usize;
        assert!(1 <= n && n <= MAX_N);
        let m = next() as usize;
        assert!(1 <= m && m <= MAX_M);
        let k = next();
        assert!(1 <= k && k <= MAX_K);
        let mut p = vec![(0usize, 0i64); m];
        for p in p.iter_mut() {
            p.0 = next() as usize;
            assert!(1 <= p.0 && p.0 <= n);
            p.0 -= 1;
            p.1 = next();
            assert!(1 <= p.1 && p.1 <= MAX_Y);
        }
        assert!(
            m.saturating_mul(k.max(p.iter().map(|p| p.1).max().unwrap()) as usize)
                <= 10usize.pow(18)
        );
        test.push((n, k, p));
    }
    test
}

fn wrong(n: usize, k: i64, p: &[(usize, i64)]) -> i64 {
    let mut dp = vec![(0, 0, 0); n];
    for &(x, y) in p.iter() {
        let po = &mut dp[x];
        po.0 += y * y;
        po.1 -= 2 * y;
        po.2 += 1;
    }
    let eval = |m: i64| -> (i64, i64) {
        if m >= 0 {
            let mut cnt = 0;
            let mut cost = 0;
            let mut zero = false;
            for &(c, b, a) in dp.iter() {
                cost += c;
                zero |= a == 0;
                if a > 0 && 0 >= a + b {
                    let x = (0 - (a + b)) / (2 * a) + 1;
                    cnt += x;
                    cost += 2 * a * (x - 1) * x / 2 + (a + b) * x;
                }
            }
            if zero {
                cnt += k;
            }
            if cnt >= k {
                return (cnt, cost);
            }
        }
        let mut cnt = 0;
        let mut cost = 0;
        let mut p = vec![0; n];
        for (p, &(c, b, a)) in p.iter_mut().zip(dp.iter()) {
            cost += c;
            if a > 0 && m >= a + b {
                let x = (m - (a + b)) / (2 * a) + 1;
                cnt += x;
                *p = x;
                cost += 2 * a * (x - 1) * x / 2 + (a + b) * x;
            }
        }
        (cnt, cost)
    };
    let mut ng = dp.iter().map(|&(_, b, a)| 2 * a + a + b - 1).min().unwrap();
    let mut ok = dp.iter().map(|&(_, b, a)| 2 * a * k + a + b).min().unwrap();
    while ok - ng > 1 {
        let mid = (ok + ng) / 2;
        if eval(mid).0 >= k {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    let (x, y) = eval(ok);
    let ans = y - ok * (x - k);
    ans
}

fn main() {
    let test = read();
    for (n, k, p) in test {
        let ans = wrong(n, k, &p);
        println!("{}", ans);
    }
}