
n = int(input()) # νκ΅ μ
answer = 0
for i in range(n):
students, apples = map(int, input().split())
answer += apples % students
print(answer)
κ°λ¨ν μλ¦¬κ° μ¬μ©λλ€.
μλ‘ λ€λ©΄ μ€λΈμκ³λ μκ°μ ꡬν λ λλ¨Έμ§μ λͺ«μ μ΄μ©νλ κ²μ μ΄μ©νλ©΄ μ½κ² λ¬Έμ μ μ κ·Όμ΄ κ°λ₯νλ€.
μ¦, λ°°μ λ μ¬κ³Ό μλ₯Ό νμ μλ‘ λλμ΄ μ€λ€λ©΄ λ¨λ μ¬κ³Όμ κ°―μλ₯Ό μ μ μλ€.