#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main () {
char a[1005], b[1005];
while (scanf("%s %s", a, b) != EOF) {
int len_a = strlen(a), len_b = strlen(b);
char res[1005];
int idx = 0, idx_a = len_a - 1, idx_b = len_b -1;
int carry ...