solucao_roger_benet.java

import java.io.*;
public class solucao{
    public static void main(String[] args)throws IOException{
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));
        int i,qtd,n,c,x;
		String[] aux;
        while(true){
            n = Integer.parseInt(in.readLine());
            if(n == 0)break;
            qtd = 0;
            for(i = 0; i < n; i++){
                aux = in.readLine().split(" ");
				c = Integer.parseInt(aux[0]);
                x = Integer.parseInt(aux[1]);
                c = (int) Math.floor(x/2);
                qtd += c;
            }
			qtd /= 2;
            out.write(qtd+"\n");
        }
        out.flush();
    }
}