You are given the number of kinds of the toys in the shop, the number of toys of each kind and cost of a toy of each kind. Find the number of toys with cost less than 50 grn.
The first line contains the number of kinds of the toys n (0≤n≤1000). Each of the next n lines contains two numbers: the number of toys a (0≤a≤1000) of the next kind and their price b (0<b≤10000) in grn.
Print the number of toys with cost less than 50 grn.