import java.util.Scanner;
import java.util.TreeMap;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext()) {
int count = Integer.parseInt(scanner.nextLine());
TreeMap<Integer, Integer> treeMap = new TreeMap<>();
while(count > 0) {
String keyValue = scanner.nextLine();
String value[] = keyValue.split(" ");
if(treeMap.containsKey(Integer.parseInt(value[0]))) {
treeMap.put(Integer.parseInt(value[0]), treeMap.get(Integer.parseInt(value[0]))+Integer.parseInt(value[1]));
} else {
treeMap.put(Integer.parseInt(value[0]), Integer.parseInt(value[1]));
}
count--;
}
treeMap.forEach((k,v) -> System.out.println(k.intValue() + " " + v.intValue()));
}
}
}