#include <bits/stdc++.h>
#define pb push_back 
using namespace std;
const int N=4e5+10;
const long long inf=-1e18;
int n,k,p,a[N];
__int128 f[N],b[N],ans=0;
vector<int> v;
void solve1()
{
    int now=0;
    long long ans=0;
    for (int i=1;i<=n;i++) cin>>a[i],a[i]-=now,ans+=abs(a[i]-k),now+=a[i]-k;
    cout<<ans;
}
void print(__int128 x)
{
    if (x>=10) print(x/10);
    putchar(x%10+'0');
}
void solve() {
    cin>>n>>k>>p;
    if (p==0)
    {
        solve1();
        return ;
    }
    p++;
    for (int i=1;i<=p;i++)
    {
        for (int j=1;j<=i;j++) v.pb(j);
        f[i]=1;
        for (int j=p;j>=p-i+1;j--) f[i]*=j;
        for (int j=i;j>=1;j--) f[i]/=j; 
    }
    for (int i=1;i<=n;i++) cin>>a[i],b[i]=k-a[i];
    for (int i=1;i<=n;i++)
    {
        for (int j=i-1;j>=max(1,i-p);j--) b[i]-=f[i-j]*b[j];
        ans+=(b[i]>0 ? b[i] : -b[i]);
    }
    print(ans);
}
int main() {
    freopen("defeat.in","r",stdin);
    freopen("defeat.out","w",stdout);
    ios::sync_with_stdio(0),cin.tie(0);
    solve();
    return 0;
}