#include <bits/stdc++.h>
using namespace std;
char buf[1 << 21], *p1 = buf, *p2 = buf;
template <class T>
void read(T &x) {
  x = 0;
  int c = getchar();
  int flag = 0;
  while (c < '0' || c > '9') flag |= (c == '-'), c = getchar();
  while (c >= '0' && c <= '9')
    x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();
  if (flag) x = -x;
}
template <class T>
T _max(T a, T b) {
  return b < a ? a : b;
}
template <class T>
T _min(T a, T b) {
  return a < b ? a : b;
}
template <class T>
bool checkmax(T &a, T b) {
  return a < b ? a = b, 1 : 0;
}
template <class T>
bool checkmin(T &a, T b) {
  return b < a ? a = b, 1 : 0;
}
const int N = 100005;
int n, m, p;
int dis[N], tim[N];
long long sumt[N];
long long dp[105][N];
void init() {
  read(n);
  read(m);
  read(p);
  dis[1] = 0;
  for (int i = 2, x; i <= n; ++i) read(x), dis[i] = dis[i - 1] + x;
  for (int i = 1, x; i <= m; ++i) read(x), read(tim[i]), tim[i] -= dis[x];
  sort(tim + 1, tim + m + 1);
  for (int i = 1; i <= m; ++i) sumt[i] = sumt[i - 1] + tim[i];
}
int rnd = 0;
int q[N];
long long dx(int ed, int st) { return ed - st; }
long long dy(int ed, int st) {
  return dp[rnd - 1][ed] + sumt[ed] - dp[rnd - 1][st] - sumt[st];
}
void solve() {
  memset(dp, 0x3f, sizeof dp);
  dp[0][0] = 0;
  for (int i = 1; i <= p; ++i) {
    dp[i][0] = 0;
    rnd = i;
    int head = 1, tail = 0;
    q[++tail] = 0;
    for (int j = 1; j <= m; ++j) {
      while (head < tail &&
             dy(q[head + 1], q[head]) <= tim[j] * dx(q[head + 1], q[head]))
        ++head;
      if (head <= tail) {
        int idx = q[head];
        dp[i][j] = dp[i - 1][idx] + (long long)tim[j] * (j - idx) -
                   (sumt[j] - sumt[idx]);
      }
      while (head < tail && dy(q[tail - 1], q[tail]) * dx(q[tail], j) >
                                dy(q[tail], j) * dx(q[tail - 1], q[tail]))
        --tail;
      q[++tail] = j;
    }
  }
  printf("%lld\n", dp[p][m]);
}
int main() {
  init();
  solve();
  return 0;
}
