Simplest Fraction

Problem Description

Compute the sum of two fractions and output it in simplest form (the denominator is not necessarily larger than the numerator). If the denominator is $0$, output error; if the denominator is $1$, the denominator need not be output; if the result is $0$, output 0 directly.

Input Format

Two fractions. For each fraction, first input the numerator, then the denominator. Both numerator and denominator are integers in the range $[0, 10^6]$.

Output Format

The simplest fraction, in the format shown in the samples. It is guaranteed that the results fit within the int range.

Sample Input 1

2 3 3 6

Sample Output 1

7/6

Sample Input 2

2 1 3 0

Sample Output 2

error

Sample Input 3

4 6 4 3

Sample Output 3

2

Sample Input 4

0 2 0 3

Sample Output 4

0