#include <bits/stdc++.h>
using namespace std;
int n, m, p, hd, tl, q[100010];
double d[100010], sd[100010], t[100010], st[100010], neko[100010],
    dp[100010][101];
inline double X(int i) { return i; }
inline double Y(int i, int k) { return dp[i][k] + st[i]; }
inline double slope(int i, int j, int k) {
  return (Y(i, k) - Y(j, k)) / (X(i) - X(j));
}
int main() {
  cin >> n >> m >> p;
  for (int i = 2; i <= n; i++) cin >> d[i], sd[i] = sd[i - 1] + d[i];
  for (int i = 1, h; i <= m; i++) cin >> h >> t[i], t[i] = double(t[i] - sd[h]);
  sort(t + 1, t + m + 1);
  for (int i = 1; i <= m; i++) st[i] = st[i - 1] + t[i];
  for (int i = 1; i <= m; i++) dp[i][1] = t[i] * i - st[i];
  for (int k = 2; k <= p; k++) {
    hd = tl = 1;
    for (int i = 1, j; i <= m; i++) {
      while (hd < tl && slope(q[hd], q[hd + 1], k - 1) < t[i]) hd++;
      j = q[hd], dp[i][k] = dp[j][k - 1] + t[i] * (i - j) - (st[i] - st[j]);
      while (hd < tl && slope(q[tl], i, k - 1) < slope(q[tl - 1], q[tl], k - 1))
        tl--;
      q[++tl] = i;
    }
  }
  cout << (long long)dp[m][p] << endl;
  return 0;
}
