diff --git a/QUSTOJ/1871.cpp b/QUSTOJ/1871.cpp
new file mode 100644
index 0000000..8089243
--- /dev/null
+++ b/QUSTOJ/1871.cpp
@@ -0,0 +1,18 @@
+#include <iostream>
+using namespace std;
+
+int main()
+{
+    int x,y,n,m;
+    cin>>x>>y>>n>>m;
+    while(m--)
+    {
+        int t;
+        cin>>t;
+        n+=t;
+        while(n<x) n+=y-x+1;
+        while(n>y) n-=y-x+1;
+        cout<<n<<endl;
+    }
+    return 0;
+}