#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define data dataa
using LL=long long;
using ULL=unsigned long long;
using LD=long double;
int f[200010],use[200010],n,m,k,stk[200010],top;
int main()
{
    scanf("%d%d%d",&n,&m,&k);
    rep(i,n)scanf("%d",&f[i]);
    use[1]=min(f[1],k);
    LL ans=use[1];
    int now=use[1];
    if(use[1]<f[1])stk[top=1]=1;
    f[n+1]=f[n+2]=0;n+=2;
    for(int i=2;i<=n;i++)
    {
        if(i-m>=1)now-=use[i-m];
        stk[++top]=i;
        for(;now<k&&top&&stk[top]>i-m;)
        {
            int tmp=min(k-now,f[stk[top]]-use[stk[top]]);
            ans+=tmp;
            now+=tmp;
            use[stk[top]]+=tmp;
            if(use[stk[top]]==f[stk[top]])top--;
        }
    }
    printf("%lld\n",ans);
    return 0;
}