#include <bits/stdc++.h>
using namespace std;
int d[100005], q[100005], t[100005];
long long dp[100005], g[100005], s[100005], sum[100005];
int main() {
  int n, m, i, k, j, p;
  while (~scanf("%d%d%d", &n, &m, &p)) {
    d[1] = 0;
    for (i = 2; i <= n; i++) scanf("%d", &d[i]), d[i] += d[i - 1];
    for (i = 1; i <= m; i++) {
      scanf("%d%d", &j, &k);
      t[i] = k - d[j];
    }
    sort(t + 1, t + m + 1);
    s[0] = 0;
    t[0] = 0;
    for (i = 1; i <= m; i++) s[i] = s[i - 1] + t[i];
    for (i = 1; i <= m; i++) dp[i] = 1LL * i * t[i] - s[i];
    dp[0] = 0;
    int f, r;
    for (i = 2; i <= p; i++) {
      f = r = 0;
      q[f++] = 0;
      for (j = 1; j <= m; j++) {
        while (f - 2 >= r) {
          int x = q[f - 1], y = q[f - 2];
          if ((dp[x] - dp[y] + s[x] - s[y]) * 1LL * (j - x) >=
              (dp[j] - dp[x] + s[j] - s[x]) * 1LL * (x - y))
            f--;
          else
            break;
        }
        q[f++] = j;
        while (r + 1 <= f - 1) {
          int x = q[r + 1], y = q[r];
          if (dp[x] - dp[y] + s[x] - s[y] <= 1LL * (x - y) * t[j])
            r++;
          else
            break;
        }
        int x = q[r];
        g[j] = min(dp[j], dp[x] + 1LL * (j - x) * t[j] - s[j] + s[x]);
      }
      for (j = 1; j <= m; j++) dp[j] = g[j];
    }
    printf("%I64d\n", dp[m]);
  }
  return 0;
}
