diff --git a/README.md b/README.md
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index 0000000000000000000000000000000000000000..3df0adca5385c635bd50b310b1b6ecebffeefbd1
--- /dev/null
+++ b/README.md
@@ -0,0 +1,11 @@
+# battle_c
+
+## Sangkyeong Lee - Team 4
+
+실전코딩2 실습
+
+## printf
+
+### stdio.h
+
+redirection stderr, stdout, stdin에 대해서 배웠음
\ No newline at end of file
diff --git a/gitignore b/gitignore
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index 0000000000000000000000000000000000000000..b883f1fdc6d69146f477bba77c117fbbd33714af
--- /dev/null
+++ b/gitignore
@@ -0,0 +1 @@
+*.exe
diff --git a/hello.c b/hello.c
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index 0000000000000000000000000000000000000000..b82f2b9208a92ca9acf9c2476ba9a497327757e3
--- /dev/null
+++ b/hello.c
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+#include <stdio.h>
+
+int main() {
+	int a;
+	fscanf(stdin, "%d", &a);
+	if (a > 0)
+		fprintf(stderr, "Error: it is positive\n");
+	else
+		fprintf(stderr, "Error: it is negative\n");
+	fprintf(stdout, "Hello World %-10d\n", a);
+
+}
+
diff --git a/input_data b/input_data
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index 0000000000000000000000000000000000000000..0180f11137031198cca443db2ad423feb76a1424
--- /dev/null
+++ b/input_data
@@ -0,0 +1 @@
+Hello World 100       
diff --git a/output_data b/output_data
new file mode 100644
index 0000000000000000000000000000000000000000..0180f11137031198cca443db2ad423feb76a1424
--- /dev/null
+++ b/output_data
@@ -0,0 +1 @@
+Hello World 100       
diff --git a/stderr.txt b/stderr.txt
new file mode 100644
index 0000000000000000000000000000000000000000..da62e877fd7f961933cac390ce56546e26623016
--- /dev/null
+++ b/stderr.txt
@@ -0,0 +1 @@
+Error: it is positive
diff --git a/stdout.txt b/stdout.txt
new file mode 100644
index 0000000000000000000000000000000000000000..0180f11137031198cca443db2ad423feb76a1424
--- /dev/null
+++ b/stdout.txt
@@ -0,0 +1 @@
+Hello World 100       
diff --git a/three_files b/three_files
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index 0000000000000000000000000000000000000000..4907bef7de34fa54a0b3bba6cb93e78a6cc32d2d
--- /dev/null
+++ b/three_files
@@ -0,0 +1 @@
+Subproject commit 4907bef7de34fa54a0b3bba6cb93e78a6cc32d2d