Final Sum

Chef has an array $A$ of length $N$. In one operation, Chef can: - Choose any subarray $[L, R]$ $(1 \leq L \leq R \leq N)$; - Add $1$ to $A_L$, subtract $1$ from $A_{L+1}$, add $1$ to $A_{L+2}$, subtract $1$ from $A_{L+3}$ and so on, till $A_R$. Chef performed $Q$ such operations where the $i^{th}$ operation was performed on the subarray $[L_i, R_i]$. Determine the final **sum** of the array af