poj 3017 Cut the Sequence dp

#include <iostream>
#include <cstdio>
#include <cstring>
#include <set>
using namespace std;
const int maxn=1e5+9;
typedef long long ll;
multiset <ll> d;
ll n,m;
int a[maxn];
struct
{
int id,data;
}que[maxn];
long long dp[maxn];
int main()
{
d.insert((ll)1<<50);
scanf("%lld %lld",&n,&m);
for(int i=1;i<=n;i++)
scanf("%d",&a[i]);

int st=1,ed=0,low=1;
long long sum=0;

for(int i=1;i<=n;i++)
{
if(a[i]>m)
{
printf("-1\n");
return 0;
}
sum+=a[i];
while(sum>m) sum-=a[low++];

while(ed>=st&&a[i]>=que[ed].data)
{
if(ed>st) d.erase(d.find(dp[que[ed-1].id]+a[que[ed].id]));
ed--;
}

if(ed>=st) d.insert(dp[que[ed].id]+a[i]);
que[++ed].data=a[i];
que[ed].id=i;
while(que[st].id<low&&ed>=st)
{
if(st<ed) d.erase(d.find(dp[que[st].id]+a[que[st+1].id]));
st++;
}

long long tmp=min(*d.begin(),dp[low-1]+que[st].data);
dp[i]=tmp;
}

printf("%lld",dp
);
return 0;
}