poj 2602 Superlong sums

#include <iostream>using namespace std;int main(){    char a[1000000], b[1000000], j;    long N, i;    cin >> N;    getchar();    for (i = 0; i < N; i++)    {        a[i] = getchar();        getchar();        b[i] = getchar();        getchar();    }    j = 0;    for (i = N - 1; i >= 0; i--)    {        a[i] += b[i] + j - 48;        j = 0;        if (a[i] > 57)        { a[i] -= 10; j = 1;        }    }    for (i = 0; i < N; i++)        putchar(a[i]);    cout << endl;    return 0;}