According to the question, as the person jumps the stairs up, there is an increase in the potential energy of the person which is provided by the work done in climbing the stairs and is given by:
Gravitational potential energy can be given by the equation PE = mgh where m is the mass, g is the gravitational constant 9.81 or 10 depending on rounding and h is the height
well weight is a force equiavlent to W= m*g
so comparing that to the potential energy equation, divide the potential energy by the height and you will get weight in Newtons