Fixing add semantics in Number

Author: VincenzoArceri

src/main/java/it/unipr/analysis/Number.java

@@ -133,7 +133,7 @@ public Number add(Number other) {
 		if (this.getType() == other.getType() && other.getType() == Type.INT)
 			return new Number(i + other.getInt());
 		if (this.getType() == other.getType() && other.getType() == Type.LONG)
-			return new Number((long) l - other.getLong());
+			return new Number((long) l + other.getLong());
 
 		BigInteger me = toBigInteger(this);
 		BigInteger ot = toBigInteger(other);