echo_program_exit.cpp added

+#include <iostream>
+#include <string>
+using namespace std;
+
+int main() {
+	string str1;
+	cin >> str1;
+	
+	if (str1 == "exit") {
+		exit(0);
+		
+	}
+	cout << str1 << endl;
+
+
+	return 0;
+}
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