#include<bits/stdc++.h>
using namespace std;
#define int long long
int a[100005];
signed main(){
    freopen("defeat.in","r",stdin);
    freopen("defeat.out","w",stdout);
    
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,k,p;
    cin>>n>>k>>p;
    for(int i = 1;i<=n;i++){
        cin>>a[i];
    }
    if(p==0){
        int ans=0;
        int fu=0;
        for(int i = 1;i<=n;i++){
            a[i]+=fu;
            ans+=abs(k-a[i]);
            fu+=k-a[i];
        }
        cout<<ans;
        return 0;
    }
    return 0;
}