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public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer in = new StringTokenizer(br.readLine());
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));

        HashMap<Long, Long> hmap = new HashMap<>();

        long total = 0;
        int n = Integer.parseInt(in.nextToken());

        for (int i = 1; i <= n; i++) {

            in = new StringTokenizer(br.readLine());
            long x = Long.parseUnsignedLong(in.nextToken());
            long y = Long.parseUnsignedLong(in.nextToken());

            long ans = hmap.getOrDefault(x, 0L);

            total += (long) i * ans;

            hmap.put(x, y);
        }

        out.println(Long.toUnsignedString(total));

        out.flush();
        out.close();
        br.close();
    }