A machine component made of a ductile material is subjected to a variable loading with $\sigma _{\text{min}}=-50$ MPa and $\sigma _{\text{max}}=-50$ MPa. If the corrected endurance limit and the yield strength for the material are $\sigma '_{e}=100$ MPa and $\sigma _{y}=300$ MPa, respectively, the factor of safety is ________.
