#include <bits/stdc++.h>
using namespace std;
int n, m, p;
long long dp[100001], s[100001], sum[100001], g[100001];
struct Node {
  int id;
  long long num;
} q[100001];
int head, tail;
int main() {
  memset(dp, 63, sizeof(dp));
  scanf("%d%d%d", &n, &m, &p);
  for (int i = 2; i <= n; i++) {
    long long x;
    scanf("%lld", &x);
    s[i] = s[i - 1] + x;
  }
  for (int i = 1; i <= m; i++) {
    long long x, y;
    scanf("%lld%lld", &x, &y);
    g[i] = y - s[x];
  }
  sort(g + 1, g + 1 + m);
  for (int i = 1; i <= m; i++) sum[i] = sum[i - 1] + g[i];
  dp[0] = 0;
  for (int i = 1; i <= p; i++) {
    head = tail = 1;
    q[1] = (Node){0, 0};
    for (int j = 1; j <= m; j++) {
      while (head < tail && g[j] * (q[head + 1].id - q[head].id) >=
                                (q[head + 1].num - q[head].num))
        head++;
      while (head < tail &&
             (dp[j] + sum[j] - q[tail].num) * (q[tail].id - q[tail - 1].id) <=
                 (q[tail].num - q[tail - 1].num) * (j - q[tail].id))
        tail--;
      q[++tail] = (Node){j, dp[j] + sum[j]};
      dp[j] = q[head].num - sum[j] + g[j] * (j - q[head].id);
    }
  }
  printf("%lld", dp[m]);
  return 0;
}
