diff --git a/20240829/B4015/B4015.cpp b/20240829/B4015/B4015.cpp
new file mode 100644
index 0000000..1e79dba
--- /dev/null
+++ b/20240829/B4015/B4015.cpp
@@ -0,0 +1,33 @@
+#include <cctype>
+#include <cstdio>
+#include <iostream>
+using namespace std;
+typedef long long ll;
+
+ll readint(){
+    int x=0,w=1;
+    char ch=0;
+    while(!isdigit(ch)){
+        if(ch=='-')w=-1;
+        ch=getchar();
+    }
+    while(isdigit(ch)){
+        x=x*10+(ch-'0');
+        ch=getchar();
+    }
+    return x*w;
+}
+
+int main(){
+    const ll n=readint(),m=readint();
+    ll ans{};
+    for(int i=1;i<=n;i++){
+        for(int j=1;j<=m;j++){
+            ll num{readint()};
+            if(i%3==2&&j%3==2){
+                ans+=num;
+            }
+        }
+    }
+    printf("%lld",ans);
+}
\ No newline at end of file
diff --git a/xmake.lua b/xmake.lua
index 90ff4a1..32030f4 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -25,4 +25,7 @@ target("lq14sd")
     add_files("20240823/十四届蓝桥比赛/数独填数.cpp")
 
 target("P2615")
-    add_files("20240828/P2615/P2615.cpp")
\ No newline at end of file
+    add_files("20240828/P2615/P2615.cpp")
+
+target("B4015")
+    add_files("20240829/B4015/B4015.cpp")
\ No newline at end of file