update

src/8/19/P1962.cpp

@@ -0,0 +1,51 @@
+#include <cstdint>
+#include <iostream>
+#include <vector>
+
+using ll = int64_t;
+
+const ll M = 1e9+7;
+
+struct M22{
+    std::vector<std::vector<ll>> v{2,std::vector<ll>(2)};
+    M22 operator*(const M22&o){
+        M22 n;
+        n.v[0][0]=(v[0][0]*o.v[0][0]%M+v[0][1]*o.v[1][0]%M)%M;
+        n.v[0][1]=(v[0][0]*o.v[0][1]%M+v[0][1]*o.v[1][1]%M)%M;
+        n.v[1][0]=(v[1][0]*o.v[0][0]%M+v[1][1]*o.v[1][0]%M)%M;
+        n.v[1][1]=(v[1][0]*o.v[0][1]%M+v[1][1]*o.v[1][1]%M)%M;
+        return n;
+    }
+    M22&operator*=(const M22&o){
+        *this= *this * o;
+        return *this;
+    }
+};
+
+M22 fpow(M22 b,ll e){
+    M22 res;
+    res.v[0][0]=res.v[1][1]=1;
+    while(e){
+        if(e&1){
+            res*=b;
+        }
+        b*=b;
+        e>>=1;
+    }
+    return res;
+}
+
+int main(){
+    ll n;
+    std::cin>>n;
+    if(n<=2){
+        std::cout<<1<<'\n';
+        return 0;
+    }
+    n-=2;
+    M22 m{{{1,1},{1,0}}};
+    m=fpow(m, n);
+    std::cout<<
+        (m.v[0][0]+m.v[0][1])%M
+    <<'\n';
+}