#include <stdio.h>
#include <string.h>
#include <math.h>

int main()
{
    int wtf, fk, p, resultlen, l1, l2, t, i, j, k, l, m, n, x, y, z, a, b, c, d, count, flag, flag1, len1, len2, flag2;
    char dum, dum2, ch, str[10000], str2[10000], min[10000], max[10000], minreal[10000], result[10000];

    scanf("%d", &t);
    scanf("%c", &dum);
    for (i = 1; i <= t; i++)
    {
        scanf("%s", str);
        scanf("%c", &dum);
        scanf("%s", str2);
        scanf("%c", &dum2);
        len1 = strlen(str);
        len2 = strlen(str2);
        flag2 = 0, wtf = 0;

        if (len1 < len2)
        {
            strcpy(min, str);
            strcpy(max, str2);
            min[len1] = '\0';
            max[len2] = '\0';
            wtf = 2;
        }
        else if (len1 > len2)
        {
            strcpy(min, str2);
            strcpy(max, str);
            min[len2] = '\0';
            max[len1] = '\0';
            wtf = 1;
        }
        else if (len1 == len2)
        {
            z = strcmp(str, str2);
            if (z < 0)
            {
                strcpy(min, str);
                strcpy(max, str2);
                min[len1] = '\0';
                max[len2] = '\0';
                wtf = 2;
            }
            else if (z > 0)
            {
                strcpy(min, str2);
                strcpy(max, str);
                min[len2] = '\0';
                max[len1] = '\0';
                wtf = 1;
            }
            else
            {
                flag2 = 5;
            }
        }

        if (flag2 == 5)
        {
            printf("0\n");
        }
        else
        {
            l1 = strlen(min);
            l2 = strlen(max);

            l = l2 - l1;
            k = 0;
            for (j = 0; j < l; j++, k++)
            {
                minreal[k] = '0';
            }
            p = 0;
            for (k = j; k < l2; k++, p++)
            {
                minreal[k] = min[p];
            }
            minreal[l2] = '\0';

            k = 0;
            p = 0;
            for (j = l2 - 1; j >= 0; j--)
            {
                x = max[j] - 48;
                y = minreal[j] - 48;
                if (k == 1)
                {
                    y = y + k;
                }
                if (x < y)
                {
                    //y = y + k;
                    x = x + 10;
                    k = 1;
                }
                else
                {
                    k = 0;
                }
                z = x - y;
                result[p] = z + 48;
                p++;
            }
            result[p] = '\0';
            resultlen = strlen(result);

            //printf("%s\n", max);
            //printf("%s\n", minreal);
            //printf("_________________\n");
            fk = 0;
            if (wtf == 2)
            {
                printf("-");
            }
            for (j = resultlen - 1; j >= 0; j--)
            {
                if (result[j] > 48)
                {
                    fk = 5;
                }
                if (fk == 5)
                {
                    printf("%c", result[j]);
                }
            }
            printf("\n");
        }
    }
    return 0;
}