diff --git a/src/10/17/P7990.cpp b/src/10/17/P7990.cpp
index 551fb5e..482cb13 100644
--- a/src/10/17/P7990.cpp
+++ b/src/10/17/P7990.cpp
@@ -12,7 +12,7 @@ const ll maxn = 2e5+5;
 ll k,m,n,f[maxn],l[maxn],r[maxn];
 struct C{
     ll p,t;
-    inline bool operator<(const C& o){
+    inline bool operator<(const C& o)const{
         return p<o.p;
     }
 }c[maxn];
diff --git a/src/10/27/yacs101.cpp b/src/10/27/yacs101.cpp
new file mode 100644
index 0000000..77fc9fe
--- /dev/null
+++ b/src/10/27/yacs101.cpp
@@ -0,0 +1,15 @@
+#include <cstdint>
+#include <iostream>
+#include <istream>
+using ll = int64_t;
+
+ll n,one,two;
+
+int main(){
+    std::iostream::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::cin>>n;
+    for(ll i=1;i<=n;i++)one+=i&1,two+=!(i&1);
+    std::cout<<one*two<<"\n";
+}
\ No newline at end of file
diff --git a/src/2/P1495.cpp b/src/2/P1495.cpp
index 2d09d04..a4cf299 100644
--- a/src/2/P1495.cpp
+++ b/src/2/P1495.cpp
@@ -1,38 +1,7 @@
 #include <cstdint>
-#include <iostream>
-#include <tuple>
-#include <vector>
-
 using ll = int64_t;
 
-std::tuple<ll,ll,ll> exgcd(const ll &a,const ll &b){
-    if(b==0){
-        ll x=1,y=0;
-        return std::make_tuple(a,x,y);
-    }
-    auto[d,x,y] = exgcd(b, a%b);
-    const ll tmpy = y;
-    y=x-a/b*y;
-    x=tmpy;
-    return std::make_tuple(d,x,y);
-}
-
-ll inv(const ll &n,const ll &p){
-    auto[d,x,y]=exgcd(n, p);
-    x=(x%p+p)%p;
-    return x;
-}
 
 int main(){
-    ll N;
-    std::cin>>N;
-    std::vector<ll> p(N),n(N);
-    for(ll i{0};i<N;i++){
-        std::cin>>p[i]>>n[i];
-    }
-    ll prod{1};
-    for(ll pi:p){
-        prod=prod*pi;
-    }
 
 }
\ No newline at end of file
diff --git a/src/2/P3811.cpp b/src/2/P3811.cpp
index 68a96b9..d8e13c8 100644
--- a/src/2/P3811.cpp
+++ b/src/2/P3811.cpp
@@ -1,21 +1,29 @@
 #include <cstdint>
 #include <iostream>
 #include <istream>
-
 using ll = int64_t;
 
-const ll maxn=3e6+5;
-ll inv[maxn];
+ll n,p;
+
+static inline ll exgcd(ll a,ll b,ll&x,ll&y){
+    if(b==0){
+        x=1;
+        y=0;
+        return a;
+    }
+    ll gcd=exgcd(b, a%b, y, x);
+    y-=a/b*x;
+    return gcd;
+}
 
 int main(){
     std::iostream::sync_with_stdio(false);
-    std::cout.tie(nullptr);
-    ll n,p;
+    std::cin.tie(nullptr);
+
     std::cin>>n>>p;
-    inv[1]=1;
-    std::cout<<1<<'\n';
-    for(ll i{2};i<=n;i++){
-        inv[i]=(p-p/i)*inv[p%i]%p;
-        std::cout<<inv[i]<<'\n';
+    for(ll i=1;i<=n;i++){
+        ll x,y;
+        exgcd(i, p, x, y);
+        std::cout<<(x%p+p)%p<<"\n";
     }
 }
\ No newline at end of file