diff --git a/day13/P1833/P1833.cpp b/day13/P1833/P1833.cpp
index 34b6847..eda87c5 100644
--- a/day13/P1833/P1833.cpp
+++ b/day13/P1833/P1833.cpp
@@ -5,7 +5,7 @@ using namespace std;
 const int MAX_N=10000+5;
 int sh,sm,eh,em,W,n;
 int w[MAX_N],v[MAX_N],c[MAX_N];
-int dp[MAX_N][MAX_N];
+int dp[MAX_N];
 
 int main(){
     ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
@@ -22,15 +22,15 @@ int main(){
     for(int i=1;i<=n;i++){
         if(c[i]==0){
             for(int j=w[i];j<=W;j++){
-                dp[i][j]=max(dp[i-1][j],dp[i][j-w[i]]+v[i]);
+                dp[j]=max(dp[j],dp[j-w[i]]+v[i]);
             }
         }else{
-            for(int j=1;j<=c[i];j++){
+            for(int j=W;j>=w[i];j--){
                 for(int k=1;k*w[i]<=j&&k<=c[i];k++){
-                    dp[i][j]=max(dp[i-1][j],dp[i-1][j-w[i]*k]+v[i]*k);
+                    dp[j]=max(dp[j],dp[j-k*w[i]]+v[i]*k);
                 }
             }
         }
     }
-    cout<<dp[n][W]<<endl;
+    cout<<dp[W]<<endl;
 }
\ No newline at end of file
diff --git a/day13/P1855/P1855.cpp b/day13/P1855/P1855.cpp
new file mode 100644
index 0000000..fde6cc7
--- /dev/null
+++ b/day13/P1855/P1855.cpp
@@ -0,0 +1,44 @@
+#include <algorithm>
+#include <cctype>
+#include <cstdio>
+#include <iostream>
+#include <ostream>
+using namespace std;
+
+const int MAX = 200+5;
+int n,M,T;
+int m[MAX],t[MAX];
+int readint();
+int dp[MAX][MAX];
+
+int main(){
+    n=readint(),M=readint(),T=readint();
+    for(int i=1;i<=n;i++){
+        m[i]=readint(),t[i]=readint();
+    }
+    for(int i=1;i<=n;i++){
+        for(int j=M;j>=1;j--){
+            for(int k=T;k>=1;k--){
+                dp[j][k] = dp[j][k];
+                if(j>=m[i]&&k>=t[i]){
+                    dp[j][k] = max(dp[j][k],dp[j-m[i]][k-t[i]]+1);
+                }
+            }
+        }
+    }
+    cout<<dp[M][T]<<endl;
+}
+
+int 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;
+}
\ No newline at end of file
diff --git a/xmake.lua b/xmake.lua
index 2923aa4..8b2060b 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -157,4 +157,8 @@ target("P1616")
 
 target("P1833")
     set_rundir("day13/P1833")
-    add_files("day13/P1833/*.cpp")
\ No newline at end of file
+    add_files("day13/P1833/*.cpp")
+
+target("P1855")
+    set_rundir("day13/P1855")
+    add_files("day13/P1855/*.cpp")
\ No newline at end of file