Writing instrument with a lateral button

A writing instrument comprising:

• a tubular body extending along a longitudinal axis between a rear end and a front end provided with an opening through which a writing tip is capable of protruding;
• a lateral button having at least one actuation face oriented radially outward and at least one first cam arranged inside said body;
• and
• a writing tip advancing mechanism comprising a movable member movable in a longitudinal direction in said body, the movable member having at least a first ramp inclined relative to the longitudinal axis,
• wherein said lateral button being capable of remaining in a rest position in which the first cam is facing the first ramp,
• wherein said lateral button being capable of making a first tilting movement toward the inside of said body during which the first cam interacts with the first ramp and the movable member makes a first movement,
• wherein said lateral button has at least a second cam longitudinally distant from the first cam, and
• wherein the movable member further comprises a bearing substantially parallel to the longitudinal axis that is adjacent to at least one second inclined ramp, the second cam resting on the bearing during the first tilting movement of said lateral button, and facing the second ramp at the end of the first tilting movement, said lateral button being capable of making a second tilting movement toward the inside of said body during which the second cam interacts with the second ramp and the movable member makes a second movement.