Prevent infinite loop in case of integer overflow.

            boolean validSolution = true;

            // do a binary search to find the max delta that won't conflict with constraints

            while(deltaMin < deltaMax) {

                final int delta = (deltaMin + deltaMax) / 2;

                // cast to long to prevent overflow.

                final int delta = (int) (((long) deltaMin + deltaMax) / 2);

                invalidateValues();

                shareOutDelta(delta, totalWeight);

                validSolution = solve(getArcs(), a, false);