#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const long long N = 1e5 + 100;
const long long K = 101;
const long long INF = 1e18;
long long d[N];
long long dp[K][N];
long long a[N], pref[N];
long long cost(long long l, long long r) {
  return a[r] * (r - l + 1) - (pref[r] - (l ? pref[l - 1] : 0));
}
void calc(long long level, long long l, long long r, long long ql,
          long long qr) {
  if (l > r) {
    return;
  }
  long long opt = -1;
  long long mid = (l + r) / 2;
  for (long long i = ql; i <= min(mid, qr); i++) {
    long long cur = cost(i, mid);
    if (i) {
      cur += dp[level - 1][i - 1];
    }
    if (dp[level][mid] > cur) {
      dp[level][mid] = cur;
      opt = i;
    }
  }
  assert(opt != -1);
  calc(level, l, mid - 1, ql, opt);
  calc(level, mid + 1, r, opt, qr);
}
signed main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  for (long long i = 0; i < K; i++) {
    for (long long j = 0; j < N; j++) {
      dp[i][j] = INF;
    }
  }
  long long n, m, k;
  cin >> n >> m >> k;
  for (long long i = 1; i < n; i++) {
    cin >> d[i];
    d[i] += d[i - 1];
  }
  for (long long i = 0; i < m; i++) {
    long long pos, time;
    cin >> pos >> time;
    long long x = d[pos - 1];
    a[i] = time - x;
  }
  sort(a, a + m);
  for (long long i = 0; i < m; i++) {
    pref[i] = a[i];
    if (i) {
      pref[i] += pref[i - 1];
    }
  }
  for (long long i = 0; i < m; i++) {
    dp[0][i] = cost(0, i);
  }
  for (long long level = 1; level < k; level++) {
    calc(level, 0, m - 1, 0, m - 1);
  }
  cout << dp[k - 1][m - 1] << '\n';
}
