#include <bits/stdc++.h>
using namespace std;
inline void setmin(int &x, int y) {
  if (y < x) x = y;
}
inline void setmax(int &x, int y) {
  if (y > x) x = y;
}
inline void setmin(long long &x, long long y) {
  if (y < x) x = y;
}
inline void setmax(long long &x, long long y) {
  if (y > x) x = y;
}
const int N = 150000;
const int inf = (int)1e9 + 1;
const long long big = (long long)1e18 + 1;
const int P = 239;
const int MOD = (int)1e9 + 7;
const int MOD1 = (int)1e9 + 9;
const double eps = 1e-9;
const double pi = atan2(0, -1);
const int ABC = 26;
struct node {
  long double ans, sum, pref, suff;
  node() {}
  node(long double x) {
    ans = pref = suff = max(x, (long double)0);
    sum = x;
  }
};
node merge(node a, node b) {
  node c;
  c.ans = max(max(a.ans, b.ans), a.suff + b.pref);
  c.sum = a.sum + b.sum;
  c.pref = max(a.pref, a.sum + b.pref);
  c.suff = max(b.suff, b.sum + a.suff);
  return c;
}
int cnt_v;
node tree[N * 4];
void build(int n, long double money[]) {
  cnt_v = 1;
  while (cnt_v < n) cnt_v <<= 1;
  for (int i = 0; i < n; i++) tree[cnt_v - 1 + i] = node(money[i]);
  for (int i = cnt_v - 2; i > -1; i--)
    tree[i] = merge(tree[i * 2 + 1], tree[i * 2 + 2]);
}
node get(int x, int lx, int rx, int l, int r) {
  if (lx >= r || l >= rx)
    return node(-big);
  else if (lx >= l && rx <= r)
    return tree[x];
  else
    return merge(get(x * 2 + 1, lx, (lx + rx) / 2, l, r),
                 get(x * 2 + 2, (lx + rx) / 2, rx, l, r));
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.precision(20);
  cout << fixed;
  int n, m, c;
  cin >> n >> m >> c;
  int x[n];
  for (int i = 0; i < n; i++) cin >> x[i];
  int p[n - 1];
  for (int i = 0; i < n - 1; i++) cin >> p[i];
  int cnt[n - 1];
  fill(cnt, cnt + n - 1, 0);
  long double money[n - 1];
  for (int i = 0; i < n - 1; i++)
    money[i] = -c * p[i] / 100.0 + (x[i + 1] - x[i]) / 2.0;
  build(n - 1, money);
  long double ans = 0;
  for (int i = 0; i < m; i++) {
    int l, r;
    cin >> l >> r;
    l--;
    r--;
    ans += get(0, 0, cnt_v, l, r).ans;
  }
  cout << ans << "\n";
  return 0;
}
