# Arup Guha
# 4/17/2026
# Solution to COP 4516 Problem: Ordering Paper

# Process cases
nC = int(input())
for loop in range(nC):

    # Store answer here, get # of exams.
    res = 0
    numE = int(input())

    # Process exams.
    for i in range(numE):
        toks = input().split()

        # Get students and pages.
        numS = int(toks[0])
        pages = int(toks[1])

        # Convert to sheets of paper.
        sheets = (pages+3)//4

        # Add for each student.
        res += (sheets*numS)

    # Ta da!
    print(res)