#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=200010;
int n,k,p;
ll a[N],ans;
int main () {
    freopen("defeat.in","r",stdin);
    freopen("defeat.out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    cin >> n >> k >> p;
    for (int i=1;i<=n;i++) cin >> a[i];
    int now=0,sum=0;
    for (int i=1;i<=n;i++) {
        now=a[i]+sum;
        ans+=abs(now-k); 
        sum+=k-now;
    }
    cout << ans <<endl;
    return 0; 
}