#include <bits/stdc++.h>
#define rep(i,l,r) for(int i=(l);i<=(r);++i)
#define per(i,r,l) for(int i=(r);i>=(l);--i)
using namespace std;
typedef long long ll;
const int N=2e5+10;
int n,m,K,a[N*2],b[N*2],f[N*2];
ll ans;
int gfa(int x){
    return f[x]^x?f[x]=gfa(f[x]):x;
}
int main(){
    // freopen("in","r",stdin);
    scanf("%d%d%d",&n,&m,&K);
    int sum=0;
    rep(i,1,n) scanf("%d",a+i),f[i]=i;
    rep(i,m+1,n+m) f[i]=n;
    rep(i,1,n+m){
        if(i>m) sum-=b[i-m];
        if(sum<n){
            int j=i;
            while(sum<K){
                if(j+m<=i||!j) break;
                int t=a[j]-b[j];
                if(sum+t>=K){
                    b[j]+=K-sum;ans+=K-sum;sum=K;
                    if(b[j]==a[j]) f[j]=j-1;
                    break;
                }
                else{
                    b[j]+=t;ans+=t;sum+=t;
                    f[j]=j-1;
                }
                j=gfa(j);
            }
        }
    }
    printf("%lld\n",ans);
    return 0;
}