diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..220c1a3
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+STEP1_Basics/*/a.out
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..acdd8ae
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "STEP1_Basics/3_Formatting/c_cross_pack"]
+	path = STEP1_Basics/3_Formatting/c_cross_pack
+	url = ssh://git@git.del.pw:2222/justuser-31/c_cross_pack.git
diff --git a/STEP1_Basics/1_Hello_world/main.c b/STEP1_Basics/1_Hello_world/main.c
new file mode 100644
index 0000000..f63f331
--- /dev/null
+++ b/STEP1_Basics/1_Hello_world/main.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main() {
+	printf("Hello world\n");
+
+	return 0;
+}
diff --git a/STEP1_Basics/2_Arithmetic/main.c b/STEP1_Basics/2_Arithmetic/main.c
new file mode 100644
index 0000000..a836d84
--- /dev/null
+++ b/STEP1_Basics/2_Arithmetic/main.c
@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <math.h>
+
+int main() {
+	float x, y;
+	printf("Enter x: "); scanf("%f", &x);
+	printf("Enter y: "); scanf("%f", &y);
+
+	float sum = x + y;
+	float sub = x - y;
+	float mult = x * y;
+	float div = x / y;
+	float poww = pow(x, y);
+	float sqrtt = pow(x, (1/y));
+
+	printf("Results:\n"
+	"sum:  %f\n"
+	"sub:  %f\n"
+	"mult: %f\n"
+	"div:  %f\n"
+	"pow:  %f\n"
+	"sqrt: %f\n",
+	sum, sub, mult, div, poww, sqrtt);
+
+	return 0;
+}
diff --git a/STEP1_Basics/3_Formatting/c_cross_pack b/STEP1_Basics/3_Formatting/c_cross_pack
new file mode 160000
index 0000000..f9a5352
--- /dev/null
+++ b/STEP1_Basics/3_Formatting/c_cross_pack
@@ -0,0 +1 @@
+Subproject commit f9a5352b6e6752375cd3520b28da474285288768
diff --git a/STEP1_Basics/3_Formatting/main.c b/STEP1_Basics/3_Formatting/main.c
new file mode 100644
index 0000000..25acfda
--- /dev/null
+++ b/STEP1_Basics/3_Formatting/main.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "c_cross_pack/libs/string.h"
+
+int main() {
+	int day, year;
+	string month = strInit("");
+
+	printf("Enter day of month: "); scanf("%d", &day);
+	printf("Enter month name: "); scanf("%s", month);
+	printf("Enter year: "); scanf("%d", &year);
+
+	string yyyy_mm_dd = strInit(int2Str(&year));
+	strAdd(&yyyy_mm_dd, "-");
+	strAdd(&yyyy_mm_dd, month);
+	strAdd(&yyyy_mm_dd, "-");
+	strAdd(&yyyy_mm_dd, int2Str(&day));
+
+	string dd_mm_yyyy = strInit(int2Str(&day));
+	strAdd(&dd_mm_yyyy, "-");
+	strAdd(&dd_mm_yyyy, month);
+	strAdd(&dd_mm_yyyy, "-");
+	strAdd(&dd_mm_yyyy, int2Str(&year));
+
+	printf("\nResult:\n");
+	printf("yyyy_mm_dd: %s\n", yyyy_mm_dd);
+	printf("dd_mm_yyyy: %s\n", yyyy_mm_dd);
+	
+	free(month);
+	
+	return 0;
+}
+
+