diff --git a/POJ/3667.cpp b/POJ/3667.cpp
new file mode 100644
index 0000000..8767cd1
--- /dev/null
+++ b/POJ/3667.cpp
@@ -0,0 +1,161 @@
+/// General includes
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+#include <algorithm>
+using namespace std;
+
+/// 区间赋值更新, 区间合并, 查找左端
+namespace AttributeSumSegmentTree
+{
+
+const int MAXN = 100100;
+const int MAXTREENODE = MAXN << 3;
+const int ATTR_BY_DEFAULT=-1;///默认初始化属性 -1 无需操作 0 子树有住户离开 1 子树有住户进入
+
+struct node
+{
+    int lt,rt;
+    int lsum,rsum,sum;
+    int attr;
+};
+
+node tree[MAXTREENODE];
+
+void build(int L,int R,int _indexer=1)
+{
+    tree[_indexer].lt=L;
+    tree[_indexer].rt=R;
+    tree[_indexer].attr=ATTR_BY_DEFAULT;
+    tree[_indexer].lsum=tree[_indexer].rsum=tree[_indexer].sum=R-L+1;
+    if(L!=R)
+    {
+        int mid=(L+R)>>1;
+        build(L,mid,_indexer<<1);
+        build(mid+1,R,_indexer<<1|1);
+    }
+}
+
+void update(int L,int R,int NewAttr,int _indexer=1)
+{
+    if(L==tree[_indexer].lt&&R==tree[_indexer].rt)
+    {
+        tree[_indexer].lsum=tree[_indexer].rsum=tree[_indexer].sum=
+            NewAttr==1 ? 0 : tree[_indexer].rt-tree[_indexer].lt+1 ; /// Same as R-L+1
+        tree[_indexer].attr=NewAttr;
+        return;
+    }
+
+    /// Push Down (updated)
+    if(tree[_indexer].attr!=-1)
+    {
+        /// Sync the Attribute to sub-tree
+        tree[_indexer<<1].attr=tree[_indexer<<1|1].attr=tree[_indexer].attr;
+        tree[_indexer].attr=-1;
+        tree[_indexer<<1].rsum=tree[_indexer<<1].lsum=tree[_indexer<<1].sum= tree[_indexer<<1].attr==1 ? 0 : tree[_indexer<<1].rt-tree[_indexer<<1].lt+1;
+        tree[_indexer<<1|1].rsum=tree[_indexer<<1|1].lsum=tree[_indexer<<1|1].sum= tree[_indexer<<1|1].attr==1 ? 0 : tree[_indexer<<1|1].rt-tree[_indexer<<1|1].lt+1;
+    }
+
+    int mid=(tree[_indexer].lt+tree[_indexer].rt)>>1;
+    if(R<=mid)
+    {
+        update(L,R,NewAttr,_indexer<<1);
+    }
+    else if(L>mid)
+    {
+        update(L,R,NewAttr,_indexer<<1|1);
+    }
+    else
+    {
+        update(L,mid,NewAttr,_indexer<<1);
+        update(mid+1,R,NewAttr,_indexer<<1|1);
+    }
+
+    /// Push Up (updated)
+    tree[_indexer].lsum=tree[_indexer<<1].lsum; /// left & left
+    tree[_indexer].rsum=tree[_indexer<<1|1].rsum; /// right & right
+
+    if(tree[_indexer<<1].lsum == tree[_indexer<<1].rt-tree[_indexer].lt+1)
+    {
+        /// Father.LeftSum == RightSon.LeftSum + LeftSon.LeftSum
+        tree[_indexer].lsum+=tree[_indexer<<1|1].lsum;
+    }
+
+    /// Why tree[_indexer].rsum but not tree[_indexer<<1|1].rsum ???
+    if(tree[_indexer].rsum==tree[_indexer<<1|1].rt-tree[_indexer<<1|1].lt+1)
+    {
+        /// Father.RightSum == LeftSon.RightSum + RightSon.RightSum
+        tree[_indexer].rsum+=tree[_indexer<<1].rsum;
+    }
+
+    tree[_indexer].sum=max(max(tree[_indexer<<1].sum,tree[_indexer<<1|1].sum),tree[_indexer<<1].rsum+tree[_indexer<<1|1].lsum);
+
+
+}
+
+int query(int Val,int _indexer=1)
+{
+    if(tree[_indexer].lt==tree[_indexer].rt)
+    {
+        return tree[_indexer].lt;
+    }
+    /// Push Down (updated)
+    if(tree[_indexer].attr!=-1)
+    {
+        /// Sync the Attribute to sub-tree
+        tree[_indexer<<1].attr=tree[_indexer<<1|1].attr=tree[_indexer].attr;
+        tree[_indexer].attr=-1;
+        tree[_indexer<<1].rsum=tree[_indexer<<1].lsum=tree[_indexer<<1].sum= tree[_indexer<<1].attr==1 ? 0 : tree[_indexer<<1].rt-tree[_indexer<<1].lt+1;
+        tree[_indexer<<1|1].rsum=tree[_indexer<<1|1].lsum=tree[_indexer<<1|1].sum= tree[_indexer<<1|1].attr==1 ? 0 : tree[_indexer<<1|1].rt-tree[_indexer<<1|1].lt+1;
+    }
+    int Mid=(tree[_indexer].rt+tree[_indexer].lt)>>1;
+    /// Left
+    if(tree[_indexer<<1].sum>=Val)
+    {
+        return query(Val,_indexer<<1);
+    }
+    /// Both Left and Right
+    else if(tree[_indexer<<1].rsum+tree[_indexer<<1|1].lsum >= Val)
+    {
+        return Mid-tree[_indexer<<1].rsum+1;
+    }
+    else /// Right
+    {
+        return query(Val,_indexer<<1|1);
+    }
+}
+
+}/// End of namespace AttributeSumSegmentTree
+
+int main()
+{
+    using namespace AttributeSumSegmentTree;
+    int N,M;
+    scanf("%d %d",&N,&M);
+    build(1,N);
+    while(M--)
+    {
+        int op;
+        scanf("%d",&op);
+        if(op==1) /// Check in
+        {
+            int x;
+            scanf("%d",&x);
+            if(tree[1].sum<x)
+            {
+                printf("0\n");continue;
+            }
+            int ans=query(x);
+            printf("%d\n",ans);
+            update(ans,ans+x-1,1);
+        }
+        else /// Check out
+        {
+            int a,b;
+            scanf("%d %d",&a,&b);
+            update(a,a+b-1,0);
+        }
+    }
+    return 0;
+}