AMC 12B 2024 Problem 5. The Sum Minimization Algorithm

In the following expression, Melanie changed some of the plus signs to minus signs:1 + 3 + 5 + 7 + ... + 97 + 99When the new expression was evaluated, it was negative. What is the least number of plus signs that Melanie could have changed to minus signs? (A) 14(B) 15(C) 16(D) 17(E) 18