#include <bits/stdc++.h>
using namespace std;
const int inf = 1000000007;
const long long linf = 1000000000000000000LL;
const double eps = 0.000001;
const double pi = 3.14159265358979323846;
template <class T>
T abs(T k) {
  return k >= 0 ? k : -k;
}
template <class T>
T sqr(T n) {
  return n * n;
}
template <class T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
template <class T>
T mod(T a, T b) {
  return (a % b + b) % b;
}
template <class T>
T addmod(T a, T b, T c) {
  return (T)((long long)(a + b) % c);
}
template <class T>
T mulmod(T a, T b, T c) {
  return (T)((long long)a * b % c);
}
template <class T>
T powmod(T a, T b, T c) {
  return (T)(b ? sqr((long long)powmod(a, b >> 1, c)) % c * (b & 1 ? a : 1) % c
               : 1);
}
template <class T>
void maxe(T &a, T b) {
  a = max(a, b);
}
template <class T>
void mine(T &a, T b) {
  a = min(a, b);
}
template <class T>
void mode(T &a, T b) {
  a = mod(a, b);
}
template <class T>
void addmode(T &a, T b, T c) {
  a = addmod(a, b, c);
}
template <class T>
void mulmode(T &a, T b, T c) {
  a = mulmod(a, b, c);
}
template <class T>
void powmode(T &a, T b, T c) {
  a = powmod(a, b, c);
}
void fileio_in_out() {
  freopen(".in", "r", stdin);
  freopen(".out", "w", stdout);
}
void fileio_txt() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
}
const int N = 111111;
int test;
int n, m, k;
long long ans;
long long d[N], h[N], t[N], s[N], st[N];
long long dp[111][N];
int q[N], head, tail;
long long f1(int i, int j, int k) { return dp[i][k] + st[k] - t[j] * k; }
long long f2(int i, int j, int k) {
  return ((dp[i][j] + st[j]) - (dp[i][k] + st[k])) / (j - k);
}
long long getans() {
  sort(t + 1, t + 1 + m);
  for (int i = 1; i <= m; i++) {
    st[i] = st[i - 1] + t[i];
    dp[1][i] = t[i] * i - st[i];
  }
  for (int i = 2; i <= k; i++) {
    head = tail = 0;
    for (int j = 1; j <= m; j++) {
      while (head < tail && f1(i - 1, j, q[head]) >= f1(i - 1, j, q[head + 1]))
        head++;
      while (head < tail &&
             f2(i - 1, q[tail - 1], q[tail]) >= f2(i - 1, q[tail], j))
        tail--;
      dp[i][j] = t[j] * j - st[j] + f1(i - 1, j, q[head]);
      q[++tail] = j;
    }
  }
  return dp[k][m];
}
int main() {
  scanf("%d%d%d", &n, &m, &k);
  for (int i = 2; i <= n; i++) {
    scanf("%I64d", &d[i]);
    s[i] = s[i - 1] + d[i];
  }
  for (int i = 1; i <= m; i++) {
    scanf("%I64d%I64d", &h[i], &t[i]);
    t[i] -= s[h[i]];
  }
  ans = getans();
  printf("%I64d\n", ans);
  return 0;
}
