#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
struct elem {
	long double l, r, total, sum;
};

const int oo = 3e5;
vector <int> a(oo);
vector <int> p(oo);
vector <long double> mo(oo);
vector <elem> b(oo * 2);
elem q;


elem sum(elem a, elem b){
	elem c;
	c.sum = a.sum + b.sum;
	c.l = max(a.l, a.sum + b.l);
	c.r = max(b.r, b.sum + a.r);
	c.total = max(max(a.total, b.total), a.r + b.l);
	return c;
}

elem gsum(int v, int ll, int rr, int l, int r){
	if (ll > r || l > rr)
		return q;
	if (l <= ll && rr <= r)
		return b[v];
	return sum(gsum(v * 2, ll, (ll + rr) / 2, l, r), gsum(v * 2 + 1, (ll + rr) / 2 + 1, rr, l, r));
}


int main(){
	int n, m, c, i, l, r, step;
	long double ans = 0, promres;
	q.total = q.l = q.r = q.sum = 0;
	cin >> n >> m >> c;
	for (i = 0; i < n; i++)
		cin >> a[i];
	for (i = 0; i < n - 1; i++)
		cin >> p[i];
	for (i = 0; i < n - 1; i++)
		mo[i] = (a[i + 1] - a[i]) / 2.0 - c * p[i] / 100.0;
	step = 1;
	while (step < n - 1)
		step *= 2;
	for (i = step; i < step + n - 1; i++){
		b[i].sum = mo[i - step];
		if (mo[i - step] > 0)
			b[i].l = b[i].r = b[i].total = mo[i - step];
	}
	for (i = step - 1; i > 0; i--){
		b[i] = sum(b[i * 2], b[i * 2 + 1]);
	}
	cout.precision(9);
	for (i = 0; i < m; i++){
		cin >> l >> r;
		promres = gsum(1, 1, step, l, r - 1).total;
		ans += promres;
	}
	cout << endl << fixed << ans;
	system("pause");
}