谢大佬，求找错误，换了行啊。全WA

#include<bits/stdc++.h>
using namespace std;
int a[1000000],n,m,ans,ma=-999999999;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	cin>>m;
	for(int i=1;i<=n;i++)
	{
		ans+=a[i];
		//cout<<i<<" "<<a[i]<<" "<<ans<<endl;
		if(i>m)
		ans-=a[i-m];
		if(ans>ma)
		ma=ans;
	}
	cout<<ma<<endl;
}