#include <bits/stdc++.h>
using namespace std;
const int INF_of_int = 1e9;
const long long INF_of_ll = 1e18;
template <typename T>
void Read(T &x) {
  bool w = 1;
  x = 0;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-') w = 0, c = getchar();
  while (isdigit(c)) {
    x = (x << 1) + (x << 3) + c - '0';
    c = getchar();
  }
  if (!w) x = -x;
}
template <typename T>
void Write(T x) {
  if (x < 0) {
    putchar('-');
    x = -x;
  }
  if (x > 9) Write(x / 10);
  putchar(x % 10 + '0');
}
const int N = 1e5 + 10;
const int K = 1e2 + 10;
long long n, m, p;
long long d[N], s[N], c[N];
long long dp[N][K];
struct Node {
  long long x, y;
} q[N];
long long operator*(const Node a, const Node b) {
  return a.x * b.y - a.y * b.x;
}
Node operator-(const Node a, const Node b) {
  return (Node){a.x - b.x, a.y - b.y};
}
long long calc(Node a, long long pos) {
  return a.y - s[pos] + c[pos] * (pos - a.x);
}
int main() {
  Read(n), Read(m), Read(p);
  for (int i = 2; i <= n; ++i) Read(d[i]), d[i] += d[i - 1];
  for (int i = 1; i <= m; ++i) {
    int t, h;
    Read(h), Read(t);
    c[i] = t - d[h];
  }
  sort(c + 1, c + m + 1);
  for (int i = 1; i <= m; ++i) {
    s[i] = s[i - 1] + c[i];
    dp[i][1] = -s[i] + i * c[i];
  }
  int l, r;
  for (int j = 2; j <= p; ++j) {
    q[l = r = 1] = (Node){0ll, 0ll};
    for (int i = 1; i <= m; ++i) {
      while (l < r && calc(q[l], i) >= calc(q[l + 1], i)) ++l;
      dp[i][j] = calc(q[l], i);
      Node now = (Node){i, dp[i][j - 1] + s[i]};
      while (l < r && (q[r] - now) * (q[r - 1] - now) > 0) --r;
      q[++r] = now;
    }
  }
  Write(dp[m][p]);
  return 0;
}
