//cout 注意精度问题 
#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define mp make_pair
#define pir pair<int,int>
#define fi first
#define se second
using namespace std;
void chkmin(int &a,int b){a=min(a,b);}
void chkmax(int &a,int b){a=max(a,b);}
inline int re()
{
    char c=getchar();
    int x=0,f=1;
    while(c<'0'||c>'9'){if(c=='-') f=-1;c=getchar();}
    while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
    return x*f;
}
const int N=100002,M=82;
int n,k,p;
int a[N];
__int128 sum[N][M];
__int128 ans;
__int128 C[M];
void print(__int128 ans)
{
    if(ans==0)
    {
        printf("0\n");
        return;
    }
    vector<int> vec;vec.clear();
    while(ans) vec.pb(ans%10),ans/=10;
    reverse(vec.begin(),vec.end());
    for(int x:vec) printf("%d",x);
    printf("\n");
    return;
}
void printfu(__int128 ans)
{
    printf("-");
    ans=-ans;
    print(ans);
    return;
}
signed main()
{
    freopen("defeat.in","r",stdin);
    freopen("defeat.out","w",stdout);
    n=re();k=re();p=re();
    C[0]=1;for(int i=1;i<=p+1;i++) C[i]=C[i-1]*(p+2-i)/i;
    C[0]=0;for(int i=2;i<=p+1;i+=2) C[i]=-C[i];
    for(int i=1;i<=n;i++) a[i]=re();
    for(int i=1;i<=n;i++)
    {
        __int128 nowadd=k-(a[i]+sum[i][p+1]);
        if(nowadd<=0) ans-=nowadd;else ans+=nowadd;
        for(int j=i+1;j<=n&&j<=i+p+1;j++) sum[j][0]+=nowadd*C[j-i];
        for(int j=1;j<=p+1;j++) sum[i+1][j]=sum[i][j]+sum[i+1][j-1];
    }
    print(ans);
    return 0;
}