Add Two Fractions
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The class Fraction of the package type.lib allow us
to manipulate fractions.  Its API can be found at the
URL http://www.eecs.yorku.ca/teaching/docs/type-api/type/lib/Fraction.html
The corresponding jar file can be found in
/cs/fac/share/classpath/type/type.jar

In this programming exercise you are asked to add
two fractions using the Fraction class.

Input
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The input consists of four integers
w x y z
with 0 <= w, y < 2^31 and 1 <= x, z < 2^31.

Output
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Print the result of (w / x) + (y / z).

Sample input
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1 2 1 4

Sample output
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3/4