#include <bits/stdc++.h>
using namespace std;
const int maxn = 100010;
const int inf = 1000100000;
struct line {
  long long a, b;
  line() {
    a = 0;
    b = 0;
  }
  line(long long c, long long d) {
    a = c;
    b = d;
  }
};
long long d[maxn];
long long t[maxn];
long long sum[maxn];
long long dp[110][maxn];
line dq[maxn];
long long calc(line a, int v) { return (long long)a.a * v + a.b; }
double calc2(line a, line b) { return (a.b - b.b) / (b.a - a.a); }
int main() {
  int n, m, p;
  scanf("%d %d %d", &n, &m, &p);
  for (int i = 2; i <= n; i++) {
    int a;
    scanf("%d", &a);
    d[i] = d[i - 1] + a;
  }
  for (int i = 1; i <= m; i++) {
    int a, b;
    scanf("%d %d", &a, &b);
    t[i] = b - d[a];
  }
  sort(t + 1, t + m + 1);
  for (int i = 1; i <= m; i++) sum[i] = sum[i - 1] + t[i];
  for (int i = 1; i <= m; i++) dp[1][i] = t[i] * i - sum[i];
  for (int i = 2; i <= p; i++) {
    int s = 0, e = 0;
    for (int j = i; j <= m; j++) {
      dq[e++] = line(-j + 1, sum[j - 1] + dp[i - 1][j - 1]);
      while (e - s >= 2 &&
             (calc2(dq[e - 1], dq[e - 3]) < calc2(dq[e - 2], dq[e - 3]))) {
        dq[e - 2] = dq[e - 1];
        e--;
      }
      while (s < e - 1 && calc(dq[s], t[j]) >= calc(dq[s + 1], t[j])) s++;
      dp[i][j] = calc(dq[s], t[j]) - sum[j] + t[j] * j;
    }
  }
  printf("%lld\n", dp[p][m]);
}
