castig

#include <bits/stdc++.h>
#define NN 100005
using namespace std;
ifstream fin("castig.in");
ofstream fout("castig.out");
int n, k, a[NN];
unsigned long long s, valmin, minmaxim;
unsigned long long int slungk[NN], slungkmaxst[NN], slungkmaxdr[NN];
int main()
{
    int i;
    fin>>n>>k;
    for(i=1; i<=n; i++)
        fin>>a[i];
    for(i=1; i<=k; i++)
        s+=a[i];
    slungk[1]=slungkmaxst[1]=s;
    for(i=2; i<=n-k+1; i++)
    {
        slungk[i]=slungk[i-1]-a[i-1]+a[i+k-1];
        slungkmaxst[i]=slungkmaxst[i-1];
        if(slungk[i]>slungkmaxst[i])
            slungkmaxst[i]=slungk[i];
    }
    slungkmaxdr[n-k+1]=slungk[n-k+1];
    for(i=n-k; i>=1; i--)
    {
         slungkmaxdr[i]=slungkmaxdr[i+1];
         if(slungk[i]>slungkmaxdr[i])
            slungkmaxdr[i]=slungk[i];
    }
    valmin=slungkmaxdr[k+1];
    for(i=2; i<=k; i++)
        if(valmin>slungkmaxdr[i+k])
            valmin=slungkmaxdr[i+k];
    for (i=k+1; i<=n-k+1; i++)
    {
        minmaxim=slungkmaxst[i-k];
        if(minmaxim<slungkmaxdr[i+k])
            minmaxim=slungkmaxdr[i+k];
        if(minmaxim<valmin)
            valmin=minmaxim;
    }
    fout<<valmin<<'\n';
    return 0;
}