#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 50;
const int inf = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
const int N = 150200;
struct node {
  double sum, maxx, maxl, maxr;
} tr[N << 2];
double X[N], f[N];
int L, R;
int n, m;
double c;
inline void update(node &a, const node &l, const node &r) {
  a.sum = l.sum + r.sum;
  a.maxl = max(l.maxl, l.sum + r.maxl);
  a.maxr = max(r.maxr, r.sum + l.maxr);
  a.maxx = max(l.maxx, r.maxx);
  a.maxx = max(a.maxx, l.maxr + r.maxl);
}
void init(int x, int l, int r) {
  if (l == r) {
    tr[x].sum = f[l];
    tr[x].maxl = tr[x].maxr = tr[x].maxx = max(0.0, f[l]);
    return;
  }
  int mid = l + r >> 1;
  init(x << 1, l, mid);
  init(x << 1 | 1, mid + 1, r);
  update(tr[x], tr[x << 1], tr[x << 1 | 1]);
}
node query(int x, int l, int r) {
  if (L <= l && r <= R) return tr[x];
  int mid = l + r >> 1;
  node tmp;
  tmp.maxx = tmp.maxl = tmp.maxr = tmp.sum = 0;
  if (R <= mid) return query(x << 1, l, mid);
  if (L > mid) return query(x << 1 | 1, mid + 1, r);
  update(tmp, query(x << 1, l, mid), query(x << 1 | 1, mid + 1, r));
  return tmp;
}
int main() {
  double p;
  int i;
  scanf("%d%d%lf", &n, &m, &c);
  for (i = 1; i <= n; i++) scanf("%lf", &X[i]);
  for (i = 1; i < n; i++) {
    scanf("%lf", &p);
    f[i] = (X[i + 1] - X[i]) / 2 - p / 100 * c;
  }
  n--;
  double ans = 0;
  init(1, 1, n);
  while (m--) {
    scanf("%d%d", &L, &R);
    R--;
    ans += query(1, 1, n).maxx;
  }
  printf("%f\n", ans);
  return 0;
}
