added echo.cpp

+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+int main() {
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+
+	// º¯¼ö ¼±¾ð
+	string str;
+
+	// echo ¼öÇà
+	cout << "input : ";
+	cin >> str;
+	cout << str;
+
+	return 0;
+}
\ No newline at end of file