#include<bits/stdc++.h>
#define Gc() getchar() 
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;using LL=__int128;
const int N=4e5+5,M=100+5,K=600+5,mod=1e9+7,Mod=mod-1;const db eps=1e-9;const int INF=1e9+7;mt19937 rnd(time(0));
int n,m,k,A[N],B[N];
void Solve(){
	int i,j;scanf("%d%d%d",&n,&m,&k);
	ll Sum=0,ans=0;
	priority_queue<pair<int,int> > q;
	for(i=1;i<=n+m;i++){
		if(i<=n) scanf("%d",&A[i]);
		q.emplace(i,A[i]);
		if(i>m) Sum-=B[i-m];
		while(Sum<k&&!q.empty()){
			auto p=q.top();q.pop();if(p.fi<=i-m) continue;
			int w=min(k-Sum,1ll*p.se);
			ans+=w;p.se-=w;B[p.fi]+=w;Sum+=w;
			if(p.se) q.emplace(p);
		}
	}
	printf("%lld\n",ans);
}
int main(){
	int t;
	// scanf("%d",&t);
	t=1;
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}