#include <bits/stdc++.h>
using namespace std;
int n, m, p;
int d[100000 + 5];
int h[100000 + 5];
int t[100000 + 5];
long long a[100000 + 5];
long long sa[100000 + 5];
long long dp[100 + 5][100000 + 5];
int head, tail;
int q[100000 + 5];
inline long long get_up(int i, int j, int k) {
  return (dp[i - 1][j] + sa[j]) - (dp[i - 1][k] + sa[k]);
}
inline long long get_down(int i, int j, int k) { return j - k; }
int main() {
  scanf("%d %d %d", &n, &m, &p);
  for (int i = 2; i <= n; i++) {
    scanf("%d", &d[i]);
    d[i] += d[i - 1];
  }
  for (int i = 1; i <= m; i++) {
    scanf("%d %d", &h[i], &t[i]);
    a[i] = t[i] - d[h[i]];
  }
  sort(a + 1, a + 1 + m);
  for (int i = 1; i <= m; i++) {
    sa[i] = sa[i - 1] + a[i];
  }
  for (int i = 1; i <= m; i++) {
    dp[0][i] = 0x3f3f3f3f3f3f3f3f;
  }
  for (int i = 1; i <= p; i++) {
    head = tail = 1;
    q[head] = 0;
    for (int j = 0; j <= m; j++) {
      while (head < tail && get_up(i, q[head + 1], q[head]) <=
                                a[j] * get_down(i, q[head + 1], q[head]))
        head++;
      dp[i][j] =
          dp[i - 1][q[head]] + a[j] * (j - q[head]) - (sa[j] - sa[q[head]]);
      while (head < tail &&
             get_up(i, q[tail], q[tail - 1]) * get_down(i, j, q[tail]) >=
                 get_up(i, j, q[tail]) * get_down(i, q[tail], q[tail - 1]))
        tail--;
      q[++tail] = j;
    }
    for (int j = 0; j <= m; j++) {
      q[j] = 0;
    }
  }
  printf("%I64d\n", dp[p][m]);
}
