truck_tour

from collections import deque

pumps_number = int(input())
fuel = 0
pumps_que = deque()
start_position = 0

for _ in range(pumps_number):
    current_fuel, distance = input().split()
    pumps_que.append((int(current_fuel), int(distance)))

current_position = 0
while current_position <= pumps_number - 1:
    is_successful = False
    fuel = 0
    for i in range(pumps_number):
        if pumps_que[i][0] + fuel >= pumps_que[i][1]:
            fuel += pumps_que[i][0]
            fuel -= pumps_que[i][1]
            is_successful = True
        else:
            start_position += 1
            fuel = 0
            is_successful = False
            break
    if not is_successful:
        pumps_que.rotate(-1)
        current_position += 1
    else:
        break

print(start_position)