N = int(input())
items = [list(map(int, input().split())) for _ in range(N)]
items.sort(key=lambda x:-x[1])

# dp[i][j] := i番目の商品まで見て、j個無料で買うことにしたときの最小値
INF = 10**18
dp = [[INF]*(N+1) for _ in range(N+1)]
dp[0][0] = 0

for i, (ai, bi) in enumerate(items, start=1):
    for j in range(i+1):
        # i個の商品のうち、j個は無料で買う => (i-j)個は有料
        dp[i][j] = min(dp[i][j], dp[i-1][j-1])
        if j < i:
            dp[i][j] = min(dp[i][j], dp[i-1][j]+ai+(i-j-1)*bi)


num = 0
day = 0
while N:
    N -= 1
    if day and N:
        N -= 1
        num += 1
    day ^= 1

print(dp[-1][num])