import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
	
	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		
		final int N = sc.nextInt();
		final long MOD = 1000000007;
		
		long sum = 0;
		for(int i = 0; i < N; i++){
			final long C = sc.nextLong();
			final long D = sc.nextLong();
			
			sum += (C + 1) / 2 * D;
			sum %= MOD;
		}
		
		System.out.println(sum);
	}
	
	public static class Scanner {
	    private BufferedReader br;
	    private StringTokenizer tok;

	    public Scanner(InputStream is) throws IOException {
	        br = new BufferedReader(new InputStreamReader(is));
	    }

	    private void getLine() throws IOException {
	        while (!hasNext()) { tok = new StringTokenizer(br.readLine()); }
	    }

	    private boolean hasNext() {
	        return tok != null && tok.hasMoreTokens();
	    }

	    public String next() throws IOException {
	        getLine(); return tok.nextToken();
	    }

	    public int nextInt() throws IOException {
	        return Integer.parseInt(next());
	    }
	    
	    public long nextLong() throws IOException {
	    	return Long.parseLong(next());
	    }
	    
	    public void close() throws IOException {
	        br.close();
	    }
	}
}