#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
typedef pair <int, int> pin;

#ifndef ONLINE_JUDGE
bool MEMORY_ST;
#endif

const int N = 1e5 + 5;
const int inf = 0x3f3f3f3f;
const ll P = 998244353LL;

int n, m, qn, mx, d[N], sd[N], h[N], q[N];
ll a[N], b[N], sum[N], f[2][N];

namespace Fread {
    const int L = 1 << 15;
    
    char buffer[L], *S, *T;
    
    inline char Getchar() {
        if(S == T) {
            T = (S = buffer) + fread(buffer, 1, L, stdin);
            if(S == T) return EOF;
        }
        return *S++;
    }
    
    template <class T> 
    inline void read(T &X) {
        char ch; T op = 1;
        for(ch = Getchar(); ch > '9' || ch < '0'; ch = Getchar())
            if(ch == '-') op = -1;
        for(X = 0; ch >= '0' && ch <= '9'; ch = Getchar()) 
            X = (X << 1) + (X << 3) + ch - '0'; 
        X *= op;
    }
    
} using Fread::read;   

inline ll yi(int cur, int i) {
    return f[cur][i] + sum[i];
}

inline ll xi(int i) {
    return i;
}

inline db slope(int c, int i, int j) {
    return 1.0 * (yi(c, i) - yi(c, j)) / (xi(i) - xi(j));
}

#ifndef ONLINE_JUDGE
bool MEMORY_ED;
#endif

int main() {
#ifndef ONLINE_JUDGE
    freopen("sample.in", "r", stdin);
    clock_t st_clock = clock();
#endif

    read(n), read(m), read(qn);
    for (int i = 2; i <= n; i++) {
        read(d[i]);
        sd[i] = sd[i - 1] + d[i];
    }
    for (int i = 1; i <= m; i++) {
        read(h[i]), read(a[i]);
        b[i] = a[i] - 1LL * sd[h[i]];
    }
    sort(b + 1, b + 1 + m);
    for (int i = 1; i <= m; i++) sum[i] = sum[i - 1] + b[i];
    for (int i = 1; i <= qn; i++) {
        int cur = i & 1, pre = cur ^ 1;
        if (i == 1) {
            for (int j = 0; j <= m; j++) f[cur][j] = 1LL * j * b[j] - sum[j];
            continue;
        }
        f[cur][0] = 0;
        int l = 1, r = 0;
        q[++r] = 0;
        for (int j = 1; j <= m; j++) {
            for (; l < r && slope(pre, q[l], q[l + 1]) < b[j]; ++l);
            f[cur][j] = f[pre][q[l]] + 1LL * (j - q[l]) * b[j] - sum[j] + sum[q[l]];
            for (; l < r && slope(pre, q[r - 1], q[r]) > slope(pre, q[r], j); --r);
            q[++r] = j;
        }
    }
    printf("%lld\n", f[qn & 1][m]);

#ifndef ONLINE_JUDGE
    clock_t ed_clock = clock();
    printf("time = %f ms\n", (double)(ed_clock - st_clock) / CLOCKS_PER_SEC * 1000);
    printf("memory = %.2f MB\n", (&MEMORY_ED - &MEMORY_ST) / 1024.0 / 1024.0);
#endif
    return 0;
}