AMC 12 2024b Problem 5

In the following expression, Melanie changed some of the plus signs to minus signs:$$1 + 3+5+7+\cdots+97+99$$When the new expression was evaluated, it was negative. What is the least number of plus signs that Melanie could have changed to minus signs?

$\textbf{(A) }14 \textbf{(B) }15 \textbf{(C) }16 \textbf{(D) }17 \textbf{(E) }18$