diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e624d96
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+.out
+.ccls
+.ccls-cache
diff --git a/alg_4_1.cpp b/alg_4_1.cpp
new file mode 100644
index 0000000..b6bad89
--- /dev/null
+++ b/alg_4_1.cpp
@@ -0,0 +1,27 @@
+#include <iostream>
+using namespace std;
+
+int gcd_recur(int n1, int n2)
+{
+	if (n1 == n2)
+	{
+		return n1;
+	}
+	
+	if (n1 > n2)
+	{
+		return gcd_recur(n1-n2, n2);
+	}
+	else
+	{
+		return gcd_recur(n1, n2-n1);
+	}
+}
+
+int main()
+{
+	int a, b;
+	cin >> a >> b;
+
+	cout << gcd_recur(a, b);
+}
\ No newline at end of file
diff --git a/alg_4_2.cpp b/alg_4_2.cpp
new file mode 100644
index 0000000..4b2f7c5
--- /dev/null
+++ b/alg_4_2.cpp
@@ -0,0 +1,17 @@
+#include <iostream>
+using namespace std;
+
+int fib(int n)
+{
+	if (n == 0) { return 1; }
+	if (n == 1) { return 1; }
+
+	return fib(n - 1) + fib(n - 2);
+}
+
+int main()
+{
+	int n; cin >> n;
+
+	cout << fib(n);
+}
\ No newline at end of file
diff --git a/alg_4_3.cpp b/alg_4_3.cpp
new file mode 100644
index 0000000..c20addc
--- /dev/null
+++ b/alg_4_3.cpp
@@ -0,0 +1,55 @@
+#include <iostream>
+using namespace std;
+
+double root(int n)
+{
+    double L, R, B;
+    L = 0; R = n;
+
+    while (fabs(R - L) > 0.00001)
+    {
+        B = (L + R) / 2;
+
+        if ( B*B > n)
+        {
+            R = B;
+        }
+        else {
+            L = B;
+        }
+    }
+    return B;
+}
+
+double root_hf_div(double n, double L, double R)
+{
+    double B;
+
+    if (fabs(R - L) < 0.00001)
+    {
+        return (L + R) / 2;
+    }
+    else
+    {
+        B = (L + R) / 2;
+
+        if ((B * B) > n)
+        {
+            return root_hf_div(n, L, B);
+        }
+        else
+        {
+            return root_hf_div(n, B, R);
+        }
+    }
+}
+
+int main()
+{
+    setlocale(LC_ALL, "Russian");
+	double n; cin >> n;
+
+    cout << "Обычный: " << root(n) << endl;
+	
+    cout << "Рекурсивный: " << root_hf_div(n, 1, n) << endl;
+}
\ No newline at end of file
diff --git a/alg_4_4.cpp b/alg_4_4.cpp
new file mode 100644
index 0000000..3507c63
--- /dev/null
+++ b/alg_4_4.cpp
@@ -0,0 +1,18 @@
+#include <iostream>
+using namespace std;
+
+int f(int n, int sum)
+{
+	if (n == 0)
+	{
+		return sum;
+	}
+	return f(n / 10, sum + n % 10);
+}
+
+int main()
+{
+	int n; cin >> n;
+
+	cout << f(n, 0);
+}
\ No newline at end of file
diff --git a/alg_4_5.cpp b/alg_4_5.cpp
new file mode 100644
index 0000000..f3e65ed
--- /dev/null
+++ b/alg_4_5.cpp
@@ -0,0 +1,15 @@
+#include <iostream>
+using namespace std;
+
+int f(int n)
+{
+	if (n == 1) { return 1; }
+	if (n % 2 == 0) { return f(n / 2); }
+	return f((n - 1) / 2) + f((n - 1) / 2 + 1);
+}
+
+int main()
+{
+	int n; cin >> n;
+	cout << f(n);
+}
\ No newline at end of file
diff --git a/alg_4_6.cpp b/alg_4_6.cpp
new file mode 100644
index 0000000..ed68bde
--- /dev/null
+++ b/alg_4_6.cpp
@@ -0,0 +1,26 @@
+#include <iostream>
+using namespace std;
+
+void move(int a, int b, int c, int n)
+{
+    if (n == 1)
+    {
+        cout << "from " << a << " to " << c << endl;
+    }
+    else
+    {
+        move(a, c, b, n - 1);
+
+        cout << "from " << a << " to " << c << endl;
+
+        move(b, a, c, n - 1);
+    }
+}
+
+int main()
+{
+    int n;
+    cout << "Enter the amount of disks: "; cin >> n;
+
+    move(1, 2, 3, n);
+}
\ No newline at end of file