DAYCON1034 C++

#include <bits/stdc++.h>
using namespace std;

int n, a[100005],k;
long long s[1000005], maxx;
void nhap()
{
    cin>>n>>k;
    //scanf("%d %d",&n,&k);
    for(int i=1;i<=n;i++)
        //scanf("%d", &a[i]);
        cin>>a[i];
}
void giai()
{
    //tinh s[1]
    for(int i=1;i<=k;i++)
          s[1]=s[1]+a[i];
    //tinh s[2], s[3], ..., s[n]
        for(int i=2;i<=n-(k-1);i++)
            s[i]=s[i-1]-a[i-1]+a[i+(k-1)];
    //tim maxx
    maxx=s[1];
    for(int i=2;i<=n-(k-1);i++)
        if(s[i]>maxx) maxx=s[i];
        //printf("%lld", maxx);
    cout<<maxx;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    freopen("DAYCON1034.inp","r",stdin);
    freopen("DAYCON1034.out","w",stdout);
    nhap();
    giai();
}