2024 AMC 12B Problem 5

In the following expression, Melanie changed some of the plus signs to minus signs:1 + 3+5+7+\cdots+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?

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

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.