diff --git a/day7/SegmentTree/2.in b/day7/SegmentTree/2.in
new file mode 100644
index 0000000..67e6303
--- /dev/null
+++ b/day7/SegmentTree/2.in
@@ -0,0 +1,6 @@
+5
+10 11 12 13 14
+3
+1 5
+5 5
+4 5
\ No newline at end of file
diff --git a/day7/SegmentTree/2.out b/day7/SegmentTree/2.out
new file mode 100644
index 0000000..9eacc6f
--- /dev/null
+++ b/day7/SegmentTree/2.out
@@ -0,0 +1,3 @@
+60
+14
+27
\ No newline at end of file
diff --git a/day7/SegmentTree/SegmentTree.cpp b/day7/SegmentTree/SegmentTree.cpp
index e69de29..67d273f 100644
--- a/day7/SegmentTree/SegmentTree.cpp
+++ b/day7/SegmentTree/SegmentTree.cpp
@@ -0,0 +1,69 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define AS(c){if(!(c)){cerr<<"assert failed: "<<#c<<endl;return -1;}}
+
+void build(int t[],int a[],int s,int e,int n){
+    if(s==e){
+        t[n]=a[s];
+        return;
+    }
+    int m=s+((e-s)>>1);
+    build(t,a,s,m,n*2);
+    build(t,a,m+1,e,n*2+1);
+    t[n]=t[n*2]+t[n*2+1];
+}
+
+int search(int t[],int s,int e,int n,int l,int r){
+    if(l<=s&&e<=r){
+        return t[n];
+    }
+    if(e<l||r<s){
+        return 0;
+    }
+    int m = s+((e-s)>>1);
+    return search(t, s, m, n*2,l, r)+search(t, m+1, e, n*2+1, l, r);
+}
+
+#ifdef OITEST
+#endif
+#ifndef OITEST
+#endif
+
+int main(int argc,char *argv[]){
+    #ifdef OITEST
+    AS(argc==3)
+    ifstream ifile(argv[1]);
+    ifstream afile(argv[2]);
+    AS(ifile.is_open()==true);
+    AS(afile.is_open()==true);
+    stringstream ss;
+    #define cout ss
+    #define cin ifile
+    #endif
+    #ifndef OITEST
+    #endif
+
+    int n;
+    cin>>n;
+    int k=n*4+1;
+    int t[k];
+    int arr[n+1];
+    for(int i=1;i<=n;i++){
+        cin>>arr[i];
+    }
+    build(t, arr, 1, n, 1);
+    int m;
+    cin>>m;
+    for(int i=1;i<=m;i++){
+        int l,r;
+        cin>>l>>r;
+        cout<<search(t, 1, n, 1, l, r)<<endl;
+        #ifdef OITEST
+        int myans,cans;
+        ss>>myans;
+        afile>>cans;
+        AS(myans==cans)
+        #endif
+    }
+}
\ No newline at end of file
diff --git a/xmake.lua b/xmake.lua
index 7ac9152..70d8d2a 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -59,7 +59,7 @@ target("P5431")
 target("segtree")
     set_rundir("./day7/SegmentTree")
     add_files("./day7/SegmentTree/*.cpp")
-    for v=1,1 do 
+    for v=1,2 do 
         local s=tostring(v)
         add_tests(s,{files="./day7/SegmentTree/*.cpp",runargs={s..".in",s..".out"},defines="OITEST"})
     end