  We study the computational complexity of short sentences in Presburger
arithmetic (Short-PA). Here by "short" we mean sentences with a bounded number
of variables, quantifiers, inequalities and Boolean operations; the input
consists only of the integer coefficients involved in the linear inequalities.
We prove that satisfiability of Short-PA sentences with $m+2$ alternating
quantifiers is $\Sigma_{P}^m$-complete or $\Pi_{P}^m$-complete, when the first
quantifier is $\exists$ or $\forall$, respectively. Counting versions and
restricted systems are also analyzed. Further application are given to hardness
of two natural problems in Integer Optimizations.
