#include <bits/stdc++.h>
#define ff first
#define ss second
using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int MAXN = 4e5;

int N, M, K, A[MAXN+10];

struct BIT
{
	ll tree[MAXN+10];
	void update(int i, ll k) { for(; i<=N; i+=(i&-i)) tree[i]+=k; }
	ll query(int i) { ll ret=0; for(; i>0; i-=(i&-i)) ret+=tree[i]; return ret; }
	ll query(int l, int r)
	{
		l=max(l, 1);
		r=min(r, N);
		return query(r)-query(l-1);
	}
}bit;

int main() {
	cin.tie(0); ios_base::sync_with_stdio(0);

	scanf("%d%d%d", &N, &M, &K);
	for(int i=1; i<=N; i++) scanf("%d", &A[i]);

	map<int, int> MM;
	for(int i=1; i<=N; i++) MM[i]=A[i];

	ll ans=0;
	for(int i=1; i<=N+M-1; i++)
	{
		int t=K-bit.query(i-M+1, i);
		for(auto it=prev(MM.upper_bound(i)); it->first>=i-M+1 && t;)
		{
			if(t>=it->second)
			{
				bit.update(it->first, it->second);
				ans+=it->second;
				t-=it->second;
				it=MM.erase(it);
				if(it==MM.begin()) break;
				it--;
			}
			else
			{
				bit.update(it->first, t);
				it->second-=t;
				ans+=t;
				break;
			}
		}
	}
	printf("%lld\n", ans);
}