//qoj362
#include <bits/stdc++.h>
using namespace std;

#define int long long

const int N = 1e5 + 10;
int n, k, T, a[N];

bool chk(int val){
    int l = k, r = k, sum = T * val * 2;
    while(l != 1 && r != n){
        int x = a[l] - a[l-1];
        int y = a[r+1] - a[r];
        if(min(x, y) > sum) return 0;
        if(x < y){
            sum = sum + T * val * 2 - x;
            -- l;
        } else {
            sum = sum + T * val * 2 - y;
            ++ r;
        }
    }
    while(l != 1){
        int x = a[l] - a[l-1];
        if(x > sum) return 0;
        sum = sum + T * val * 2 - x;
        -- l;
    }
    while(r != n){
        int y = a[r+1] - a[r];
        if(y > sum) return 0;
        sum = sum + T * val * 2 - y;
        ++ r;
    }
    return 1;
}

signed main(){
    scanf("%lld%lld%lld", &n, &k, &T);
    for(int i = 1; i <= n; ++ i){
        scanf("%lld", &a[i]);
    }
    int l = 0, r = 1e9;
    while(l < r){
        int mid = l + r >> 1;
        if(chk(mid)){
            r = mid;
        } else {
            l = mid + 1;
        }
    }
    printf("%lld\n", l);
    return 0;
}