为何开o2会re

#include <bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int n,x,a[N],c[N],mid;
int ff() {
    stack<int> stk;
	for(register int i=1;i<=n;i++){
		c[i]=0;
	}
    a[0]=c[0]=a[n]=INT_MAX;
    for(register int i=1;i<mid;i++) stk.push(i);
    for(register int i=0;i<n;i++){
        if(a[i+mid]&&i+mid<=n) stk.push(i+mid);
        while(c[i]&&!stk.empty()&&stk.top()>i){
            int t=stk.top();
            int minn=min(c[i],a[t]-c[t]);
            c[i]-=minn;
            c[t]+=minn;
            if(c[t]==a[t]) stk.pop();
        }
    }
    return c[n];
}
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
    cin>>n>>x;
    for(register int i=1;i<=n-1;i++){
    	cin>>a[i];
	}
    int l=1,r=n,cnt;
    while(l<=r){
        mid=(l+r)/2;
        if (ff()>=2*x){
            cnt=mid;
            r=mid-1;
        }else l=mid+1;
    }
    cout<<cnt;
    return 0;
}