#include <bits/stdc++.h>
using namespace std;
const int N = 105000;
const int M = 105;
int n, m, p;
long long hill[N];
long long a[N], s[N];
long long dp[N];
int top, tail;
long long duix[N], duiy[N];
int getint() {
  char e = getchar();
  int res = 0;
  while (e < '0' || e > '9') e = getchar();
  while ('0' <= e && e <= '9') {
    res = (res << 3) + (res << 1) + e - '0';
    e = getchar();
  }
  return res;
}
int main() {
  int i, j;
  n = getint();
  m = getint();
  p = getint();
  for (i = 2; i <= n; i++) hill[i] = getint();
  for (i = 2; i <= n; i++) hill[i] += hill[i - 1];
  for (i = 1; i <= m; i++) {
    a[i] = -hill[getint()];
    a[i] += getint();
  }
  sort(a + 1, a + m + 1);
  for (i = 1; i <= m; i++) s[i] = a[i] + s[i - 1];
  for (i = 1; i <= m; i++) dp[i] = i * a[i];
  for (j = 2; j <= p; j++) {
    top = 1;
    tail = 0;
    for (i = 1; i <= m; i++) {
      long long nowx = i;
      long long nowy = dp[i];
      while (tail >= 2) {
        double xla = duiy[tail] - duiy[tail - 1];
        xla /= duix[tail] - duix[tail - 1];
        double xlb = nowy - duiy[tail - 1];
        xlb /= nowx - duix[tail - 1];
        if (xla - xlb > -1e-10)
          tail--;
        else
          break;
      }
      tail++;
      duix[tail] = nowx;
      duiy[tail] = nowy;
    }
    for (i = 1; i <= m; i++) {
      dp[i] = duiy[top] - a[i] * duix[top];
      while (top < tail && duix[top + 1] <= i) {
        long long now = duiy[top + 1] - a[i] * duix[top + 1];
        if (now <= dp[i]) {
          top++;
          dp[i] = now;
        } else
          break;
      }
      dp[i] += i * a[i];
    }
  }
  printf("%I64d\n", dp[m] - s[m]);
  return 0;
}
