#include <bits/stdc++.h>
#define all(x) x.begin(),x.end()
const int inf=1e9;
using i64 = long long;
#define int long long
struct interval
{
int l,r;
};
std::vector<interval> add_range(std::vector<interval> a,int k)
{
std::vector<interval>rez;
std::map<int,int>mp;
for(auto &c:a)
{
mp[c.l-k]++;
mp[c.r+k+1]--;
}
int last=-1,sum=0;
for(auto &c:mp)
{
if(sum==0)
{
last=c.first;
}
sum+=c.second;
if(sum==0)
{
rez.push_back({last , c.first-1});
}
}
return rez;
}
std::vector<interval> unite(std::vector<interval>a,std::vector<interval> b)
{
std::vector<interval>rez;
std::map<int,int>mp;
for(auto &c:a)
{
mp[c.l]++;
mp[c.r+1]--;
}
for(auto &c:b)
{
mp[c.l]++;
mp[c.r+1]--;
}
int last=-1,sum=0;
for(auto &c:mp)
{
if(sum==0)
{
last=c.first;
}
sum+=c.second;
if(sum==0)
{
rez.push_back({last , c.first-1});
}
}
return rez;
}
std::vector<interval> intersect(std::vector<interval>a,std::vector<interval> b)
{
std::vector<interval>rez;
std::map<int,int>mp;
for(auto &c:a)
{
mp[c.l]++;
mp[c.r+1]--;
}
for(auto &c:b)
{
mp[c.l]++;
mp[c.r+1]--;
}
int last=-1,sum=0;
for(auto &c:mp)
{
int last_sum=sum;
sum+=c.second;
if(last_sum<2 && sum==2)
{
last=c.first;
}
if(sum<2 && last_sum==2)
{
rez.push_back({last,c.first-1});
}
}
return rez;
}
main()
{
int n,k,t;
std::cin>>n>>k>>t;
k--;
std::vector<int>a(n);
for(auto &c:a)
{
std::cin>>c;
}
auto test=[&](int s)->bool
{
std::vector<std::vector<std::vector<interval>>>dp(n,std::vector<std::vector<interval>>(n));
dp[k][k]={{a[k],a[k]}};
for(int l=n-1;l>=0;l--)
{
for(int r=l+1;r<n;r++)
{
auto ll=intersect(add_range(dp[l][r-1],t*s) , {{a[r]-(r-l)*t*s,a[r]+(r-l)*t*s}});
auto rr=intersect(add_range(dp[l+1][r],t*s) , {{a[l]-(r-l)*t*s,a[l]+(r-l)*t*s}});
dp[l][r]=unite(ll , rr);
assert(dp[l][r].size()<=1);
}
}
return dp[0][n-1].size()>0;
};
int st=0,dr=a.back(),rez=-1;
while(st<=dr)
{
int mid=(st+dr)/2;
if(test(mid))
{
dr=mid-1;
rez=mid;
}
else
{
st=mid+1;
}
}
assert(rez!=-1);
std::cout<<rez;
return 0;
}
/*
2 1 10
200
300
*/
