Manchester police are looking for a man who robbed a city convenience store Friday night with a gun. Police said the man entered the 61 Market at 61 Maple St. about 6:45 p.m., threatened the clerk with a gun and made off with an undisclosed amount of cash. A police K-9 searched the area, but the man wasn't located, Manchester police said in a press release.The man is described as white, between 5 feet 8 inches and 5 feet 10 inches, and in his 20s. He was wearing a black mask and black-hooded sweatshirt.Anyone with information is asked to contact the Manchester Police Crimeline at 603-624-4040.