diff --git a/src/2/P2455.cpp b/src/2/P2455.cpp
new file mode 100644
index 0000000..0fc6a7d
--- /dev/null
+++ b/src/2/P2455.cpp
@@ -0,0 +1,123 @@
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <iomanip>
+#include <ios>
+#include <iostream>
+#include <random>
+#include <utility>
+
+using ll = int64_t;
+
+constexpr ll maxn=50;
+ll n;
+double m[maxn+5][maxn+5];
+
+void sp(double *a,double* b){
+    for(ll i=1;i<=n+1;i++){
+        std::swap(a[i],b[i]);
+    }
+}
+
+void pm(){
+    for(ll i=1;i<=n;i++){
+        for(ll j=1;j<=n+1;j++){
+            std::cout<<m[i][j]<<' ';
+        }
+        std::cout<<'\n';
+    }
+    std::cout<<'\n';
+}
+
+bool isz(double a){
+    if(a > 1e-8 || a<-1e-8){
+        return false;
+    }
+    // if(a!=0){
+    //     return false;
+    // }
+    return true;
+}
+
+int main(){
+    ll rank = 0;
+    std::cin>>n;
+    for(ll i=1;i<=n;i++){
+        for(ll j=1;j<=n+1;j++){
+            std::cin>>m[i][j];
+        }
+    }
+    // std::random_device rd{};
+    // std::uniform_int_distribution<ll> uid(1,n);
+    // ll asp[maxn];
+    // for(ll i=1;i<=n;i++){
+    //    asp[i]=uid(rd);
+    // }
+    // for(ll i=1;i<=n/2;i++){
+    //     sp(m[i],m[asp[i]]);
+    // }
+    // pm();
+
+    for(ll i=1;i<=n;i++){
+        static ll nowused{1};    
+        ll maxnj=nowused;
+        for(ll j=nowused+1;j<=n;j++){
+            if(std::abs(m[j][i])>std::abs(m[maxnj][i])){
+                maxnj=j;
+            }
+        }
+        if(isz(m[maxnj][i]))continue;
+        else{
+            nowused++;
+        }
+        if(maxnj!=i){
+            sp(m[i],m[maxnj]);
+        }
+        double fact = m[i][i];
+        for(ll j=1;j<=n+1;j++){
+            m[i][j]/=fact;          
+        }
+        for(ll k=i+1;k<=n;k++){
+            if(k==i)continue;
+            double fact = m[k][i];
+            for(ll j=1;j<=n+1;j++){
+                m[k][j]-=m[i][j]*fact;
+            }
+        }
+    }
+    // pm();
+    bool isfy=false,isl=false;
+    for(ll i=1;i<=n;i++){
+        bool isAZ=true;
+        for(ll j=1;j<=n;j++){
+            if(!isz(m[i][j])){
+                isAZ=false;
+                break;
+            }
+        }
+        for(ll i=1;i<=n;i++){
+            if(std::isnan(m[i][n+1])){
+                isl=true;
+                return 0;
+            }
+        }
+        if(isAZ){
+            if(isz(m[i][n+1])){
+                isl=true;
+            }else{
+                isfy=true;
+            }
+        }
+    }
+    if(isfy){
+        std::cout<<"-1\n";
+        return 0;
+    }
+    if(isl){
+        std::cout<<"0\n";
+        return 0;
+    }
+    for(ll i=1;i<=n;i++){
+        std::cout<<std::fixed<<std::setprecision(0)<<"x"<<i<<"="<<std::fixed<<std::setprecision(2)<<m[i][n+1]<<'\n';
+    }
+}
diff --git a/src/2/P3389.cpp b/src/2/P3389.cpp
new file mode 100644
index 0000000..630f422
--- /dev/null
+++ b/src/2/P3389.cpp
@@ -0,0 +1,83 @@
+#include <cmath>
+#include <cstdint>
+#include <iomanip>
+#include <ios>
+#include <iostream>
+#include <utility>
+
+using ll = int64_t;
+template<class T>
+T read(){
+    T t;
+    std::cin>>t;
+    return t;
+}
+constexpr ll maxn = 100;
+ll n;
+double im[maxn+5][maxn+5],tmp[maxn+5];
+void cp(double*f,double*t){
+    for(ll i=1;i<=n+1;i++){
+        t[i]=f[i];
+    }
+}
+void sp(double*f,double*t){
+    for(ll i=1;i<=n+1;i++){
+        std::swap(f[i],t[i]);
+    }
+}
+int main(){
+    std::cin>>n;
+    for(ll i=1;i<=n;i++){
+        for(ll j=1;j<=n+1;j++){
+            std::cin>>im[i][j];
+        }
+    }
+    for(ll i=1;i<=n;i++){
+        for(ll k=i;k<=n;k++){
+            if(im[k][i]!=0){
+                if(k!=i){
+                    sp(im[k],im[i]);
+                }
+                break;
+            }
+        }
+        double fact = im[i][i];
+        for(ll j=1;j<=n+1;j++){
+            im[i][j]/=fact;
+        }
+        for(ll k=1;k<=n;k++){
+            if(k==i)continue;
+            double fact = im[k][i];
+            for(ll j=1;j<=n+1;j++){
+                im[k][j]-=fact*im[i][j];
+            }
+        }
+    }
+
+    if([]()->bool{
+        for(ll i=1;i<=n;i++){
+            bool isAllZero=true;
+            for(ll j=1;j<=n;j++){
+                if(im[i][j]!=0){
+                    isAllZero=false;
+                }
+            }
+            if(isAllZero){
+                return false;
+            }
+        }
+        for(ll i=1;i<=n;i++){
+            if(std::isnan(im[i][n+1])){
+                return false;
+            }
+        }
+        return true;
+    }()){
+        std::cout<<std::fixed<<std::setprecision(2);
+        for(ll i=1;i<=n;i++){
+            std::cout<<im[i][n+1]<<'\n';
+        }
+    }else{
+        std::cout<<"No Solution\n";
+    }
+}
\ No newline at end of file