#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <deque>

using namespace std;

typedef long long ll;

int n, m, k;
ll a[111111];

ll dp[333][33];

ll dp2[2][333];

ll dp3[111111][333];
priority_queue<ll> q[333], dq[333];

ll dp4[333][111111];
int deq[333][111111];
int s[333], t[333];

struct S {
  
};

int main(void) {
  scanf("%d%d%d", &n, &m, &k);
  for (int i = 0; i < n; i++) {
    scanf("%lld", a+i);
  }
  if (n == m) {
    ll res = 0;
    memset(dp2, -1, sizeof(dp2));
    dp2[1][0] = 0;
    for (int i = 0; i < n; i++) {
      dp2[i%2][0] = 0;
      for (int j = 1; j <= k; j++) {
        if (dp2[i%2][j-1] >= 0) {
          dp2[(i+1)%2][j] = max({
                dp2[(i+1)%2][j],
                    dp2[i%2][j-1] + a[i]*j,
                    dp2[i%2][j]
                  });
        }
      }
      for (int j = 0; j <= k; j++) {
        res = max(res, dp2[(i+1)%2][j]);
        if (dp2[i%2][j] >= 0) {
          dp2[i%2][j] = 0;
        }
        // printf("%5lld", dp2[(i+1)%2][j]);
      }
      // puts("");
    }
    printf("%lld\n", res);
  } else if (n <= 300 && k <= 30) {
    memset(dp, -1, sizeof(dp));
    for (int i = 0; i <= n; i++) {
      dp[i][0] = 0;
    }
    for (int i = 1; i <= n; i++) {
      for (int j = 0; j < k; j++) {
        for (int l = 1; l <= m && i-l >= 0; l++) {
          if (dp[i-l][j] >= 0) {
            dp[i][j+1] = max(dp[i][j+1],
                             dp[i-l][j]+a[i-1]*(j+1));
          }
        }
      }
    }
    ll res = 0;
    for (int i = 0; i <= n+1; i++) {
      for (int j = 0; j <= k; j++) {
        // printf("%5lld", dp[i][j]);
        res = max(res, dp[i][j]);
      }
      // puts("");
    }
    printf("%lld\n", res);
  } else if (k <= 30) {
    q[0].push(0);
    memset(dp3, -1, sizeof(dp3));
    for (int i = 1; i <= n; i++) {
      for (int j = k-1; j >= 0; j--) {
        if (q[j].size() == 0) continue;
        while (!dq[j].empty() && q[j].top() == dq[j].top()) {
          q[j].pop();
          dq[j].pop();
        }
        dp3[i][j+1] = q[j].top()+a[i-1]*(j+1);
        q[j+1].push(q[j].top()+a[i-1]*(j+1));
      }
      if (i-m >= 0) {
        for (int j = 0; j < k; j++) {
          if (dp3[i-m][j] >= 0) {
            dq[j].push(dp3[i-m][j]);
          }
        }
      }
    }
    printf("%lld\n", q[k].top());
  } else {
    memset(dp4, -1, sizeof(dp4));
    for (int i = 0; i <= n; i++) {
      dp4[0][i] = 0;
      deq[0][t[0]++] = 0;
    }
    ll res = 0;
    for (int i = 1; i <= n; i++) {
      for (int j = k-1; j >= 0; j--) {
        if (s[j] < t[j]) {
          dp4[j+1][i] = dp4[j][deq[j][s[j]]] + a[i-1]*(j+1);
          res = max(res, dp4[j+1][i]);
          // printf("%d %d max: %lld\n", i, j, dp4[j][deq[j][s[j]]]);
          while (s[j+1] < t[j+1] &&
                 dp4[j+1][deq[j+1][t[j+1]-1]] <= dp4[j+1][i]) --t[j+1];
          deq[j+1][t[j+1]++] = i;
          if (i-m >= 0) {
            if (j > 0 && deq[j][s[j]] == i-m) {
              ++s[j];
            }
          }
        }
      }
    }
    /*
    for (int ii = 0; ii <= k; ii++) {
      for (int jj = 0; jj <= n; jj++) {
        printf("%5lld", dp4[ii][jj]);
      }
      puts("");
    }
    // */
    printf("%lld\n", res);
  }
  return 0;
}


Measured memory_bytes: 408320