diff --git a/HDOJ/1556_acm_davidcn.cpp b/HDOJ/1556_acm_davidcn.cpp
new file mode 100644
index 0000000..8a107ef
--- /dev/null
+++ b/HDOJ/1556_acm_davidcn.cpp
@@ -0,0 +1,53 @@
+#include<stdio.h>
+#include<string.h>
+#define MAXN 100005
+struct ST
+{
+	int l,r,sum;
+}st[MAXN*3];
+int nn;
+void build(int ll,int rr,int n)
+{
+	st[n].l=ll;
+	st[n].r=rr;
+	st[n].sum=0;
+	if (ll==rr) return ;
+	int mid=(ll+rr)/2;
+	build(ll,mid,2*n);
+	build(mid+1,rr,2*n+1);
+};
+void color(int ll,int rr,int n)
+{
+	if (st[n].l==ll&&st[n].r==rr) {st[n].sum++;return ;}
+	int mid=(st[n].l+st[n].r)/2;
+	if (rr<=mid) color(ll,rr,2*n);
+	else
+	if (ll>=mid+1) color(ll,rr,2*n+1);
+	else
+	{
+		color(ll,mid,2*n);
+		color(mid+1,rr,2*n+1);
+	}
+}
+void out(int n,int sum)
+{
+	if (st[n].l==st[n].r) {printf("%d",sum+st[n].sum);if (st[n].l!=nn) printf(" ");return;}
+	out(2*n,sum+st[n].sum);
+	out(2*n+1,sum+st[n].sum);
+}
+int main()
+{
+	int i,p,q;
+	while (scanf("%d",&nn)&&nn)
+	{
+		build(1,nn,1);
+		for (i=1;i<=nn;++i)
+		{
+			scanf("%d%d",&p,&q);
+			color(p,q,1);
+		}
+		out(1,0);
+		printf("/n");
+	}
+	return 0;
+}