fix OpenBSD arith
fix OpenBSD arith

tectronics/ypsilon,paines/ypsilon,letoh/ypsilon,tectronics/ypsilon,paines/ypsilon,suhorng/ypsilon-fork,suhorng/ypsilon-fork,letoh/ypsilon,suhorng/ypsilon-fork,fujita-y/ypsilon,david135/ypsilon,paines/ypsilon,david135/ypsilon,david135/ypsilon,letoh/ypsilon,fujita-y/ypsilon