#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:256777216")
using namespace std;
inline long long aabs(long long a) {
  if (a < 0) return -a;
  return a;
}
inline int aabs(int a) {
  if (a < 0) return -a;
  return a;
}
long long mulmod(long long a, long long b, long long MOD) {
  if (b == 0) return 0;
  long long res = mulmod(a, b >> 1, MOD);
  res += res;
  res %= MOD;
  return (b & 1) ? (a + res) % MOD : res;
}
long long gcd(long long a, long long b) {
  while (a != 0 && b != 0) {
    if (a > b) {
      a %= b;
    } else {
      b %= a;
    }
  }
  return a + b;
}
long long pow(long long a, long long n, long long m) {
  if (n == 0) {
    return 1 % m;
  }
  long long t = pow(a, n / 2, m);
  t = (t * t) % m;
  if (n & 1) {
    t = (t * a) % m;
  }
  return t;
}
inline bool islet(char ch) {
  return ('a' <= ch && ch <= 'z') || ('A' <= ch && ch <= 'Z');
}
inline bool isdigit(char ch) { return ('0' <= ch && ch <= '9'); }
struct data {
  double sum, pref, suff, ans;
};
double s[200000];
int n;
data t[800000];
data combine(data l, data r) {
  data res;
  res.sum = l.sum + r.sum;
  res.pref = max(l.pref, l.sum + r.pref);
  res.suff = max(r.suff, r.sum + l.suff);
  res.ans = max(max(l.ans, r.ans), l.suff + r.pref);
  return res;
}
data make_data(double val) {
  data res;
  res.sum = val;
  res.pref = res.suff = res.ans = max(0.0, val);
  return res;
}
void build(int v, int tl, int tr) {
  if (tl == tr)
    t[v] = make_data(s[tl]);
  else {
    int tm = (tl + tr) / 2;
    build(v * 2, tl, tm);
    build(v * 2 + 1, tm + 1, tr);
    t[v] = combine(t[v * 2], t[v * 2 + 1]);
  }
}
data query(int v, int tl, int tr, int l, int r) {
  if (l == tl && tr == r) return t[v];
  int tm = (tl + tr) / 2;
  if (r <= tm) return query(v * 2, tl, tm, l, r);
  if (l > tm) return query(v * 2 + 1, tm + 1, tr, l, r);
  return combine(query(v * 2, tl, tm, l, tm),
                 query(v * 2 + 1, tm + 1, tr, tm + 1, r));
}
int main() {
  ios::sync_with_stdio(0);
  cout.setf(ios::fixed);
  cout.precision(6);
  int m, c;
  int x[200000];
  cin >> n >> m >> c;
  for (int i = 0; i < n; i++) {
    cin >> x[i];
  }
  int p[200000];
  p[0] = 0;
  for (int i = 1; i < n; i++) {
    cin >> p[i];
  }
  s[0] = 0;
  for (int i = 1; i < n; i++) {
    s[i] = (x[i] - x[i - 1]) / 2.0 - c * p[i] / 100.0;
  }
  build(1, 0, n - 1);
  double ans = 0;
  for (int i = 0; i < m; i++) {
    int t1, t2;
    cin >> t1 >> t2;
    data tmp = query(1, 0, n - 1, t1, t2 - 1);
    ans += tmp.ans;
  }
  cout << ans;
  return 0;
}
