#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
struct line {
  long long m, c;
  long long eval(long long x) { return m * x + c; }
  long long div(long long a, long long b) {
    return a / b - ((a ^ b) < 0 && a % b);
  }
  long long intersectX(line l) { return div(c - l.c, l.m - m); }
};
struct LineContainerFast {
  vector<line> v;
  int start, end;
  LineContainerFast() {
    start = 0;
    end = -1;
  }
  void add(long long m, long long c) {
    line l = {m, c};
    while (start < end && l.intersectX(v[end]) >= v[end].intersectX(v[end - 1]))
      --end;
    if (++end == v.size())
      v.push_back(l);
    else
      v[end] = l;
  }
  long long query(long long x) {
    assert(start <= end);
    while (start < end && v[start].eval(x) <= v[start + 1].eval(x)) ++start;
    return v[start].eval(x);
  }
  void clear() {
    v.clear();
    start = 0;
    end = -1;
  }
  int size() { return end - start + 1; }
};
void solve() {
  int n, m, P, h;
  long long t;
  cin >> n >> m >> P;
  int d[n];
  d[0] = 0;
  for (int i = 1; i < n; i++) {
    cin >> d[i];
    d[i] += d[i - 1];
  }
  vector<long long> cat(m);
  for (int i = 0; i < m; i++) {
    cin >> h >> t;
    cat[i] = t - d[h - 1];
  }
  sort((cat).begin(), (cat).end());
  long long dp[m], sum = 0;
  for (int i = 0; i < m; i++) {
    dp[i] = cat[i] * i - sum;
    sum += cat[i];
  }
  long long suff[m + 1], tmp;
  suff[m] = 0;
  for (int i = m - 1; i >= 0; i--) suff[i] = suff[i + 1] + cat[i];
  LineContainerFast l;
  for (int p = 2; p <= P; p++) {
    l.clear();
    for (int i = 0; i < p - 1; i++) l.add(-i, suff[i + 1]);
    for (int i = p - 1; i < m; i++) {
      tmp = dp[i];
      dp[i] = i * cat[i] + suff[i + 1] - l.query(-cat[i]);
      l.add(-i, suff[i + 1] - tmp);
    }
  }
  cout << dp[m - 1] << "\n";
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  solve();
}
