#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
const long long INF = 1e18;
struct Line {
  long long k, b;
  Line(long long k, long long b) : k(k), b(b) {}
  Line() : k(0), b(0) {}
  pair<long double, long double> intr(Line line) {
    pair<long double, long double> ans;
    ans.first = (long double)(line.b - b) / (k - line.k);
    ans.second = k * ans.first + b;
    return ans;
  }
};
struct CHT {
  vector<long double> stk;
  vector<Line> stl;
  long long get(long long x) {
    long long num =
        lower_bound((stk).begin(), (stk).end(), x) - stk.begin() - 1;
    return stl[num].b + stl[num].k * x;
  }
  bool check(Line l) {
    auto [x, y] = l.intr(stl.back());
    if (x < stk.back()) return true;
    return false;
  }
  void add(Line t) {
    if (!(long long)((stk).size())) {
      stk.push_back(-INF);
      stl.push_back(t);
      return;
    }
    while ((long long)((stk).size()) && check(t))
      stk.pop_back(), stl.pop_back();
    auto [x, y] = t.intr(stl.back());
    stk.push_back(x), stl.push_back(t);
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, m, p;
  cin >> n >> m >> p;
  vector<long long> a(m), h(m), t(m), d(n - 1), dp(m, 0), s(n, 0), pref(m, 0);
  for (auto &e : d) cin >> e;
  for (long long i = 0; i < m; i++) cin >> h[i] >> t[i];
  for (long long i = 1; i < n; i++) s[i] = s[i - 1] + d[i - 1];
  for (long long i = 0; i < m; i++) a[i] = t[i] - s[h[i] - 1];
  sort((a).begin(), (a).end());
  pref[0] = a[0];
  for (long long i = 1; i < m; i++) pref[i] = pref[i - 1] + a[i];
  dp[0] = 0;
  for (long long i = 1; i < m; i++) dp[i] = -pref[i] + a[i] * (i + 1);
  for (long long k = 0; k < p - 1; k++) {
    vector<long long> dp2(m, INF);
    dp2[0] = 0;
    CHT kek;
    kek.add({0, pref[0]});
    for (long long j = 1; j < m; j++) {
      dp2[j] = kek.get(a[j]) + a[j] * j - pref[j];
      kek.add({-j, dp[j] + pref[j]});
    }
    swap(dp, dp2);
  }
  cout << dp[m - 1];
}
