#include<bits/stdc++.h>
using namespace std;
long long n,k,p,m,a[100005],c[200005][85],ps,op,as;
int main(){
    freopen("defeat.in","r",stdin);
    freopen("defeat.out","w",stdout);
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>k>>p,m=n+p+3,c[0][0]=1;
    for(int i=1;i<=n;i++) cin>>a[i];
    if(!p){
        for(int i=1;i<=n;i++){
            a[i]+=ps;
            as+=abs(a[i]-k);
            ps+=k-a[i]; 
        }
        cout<<as;
        return 0;
    }
    for(int i=1;i<=m;i++){
        c[i][0]=1;
        for(int j=1;j<=p;j++){
            c[i][j]=c[i-1][j-1]+c[i-1][j];
        }
    }
    for(int i=1;i<=n;i++){
        if(a[i]>k){
            ps=a[i]-k,as+=ps;
            for(int j=i;j<=n;j++) a[j]-=c[j-i+p][p]*ps;
        }else if(a[i]<k){
            ps=k-a[i],as+=ps;
            for(int j=i;j<=n;j++) a[j]+=c[j-i+p][p]*ps;
        }
    }
    cout<<as;
    return 0;
}