import sys
input = sys.stdin.readline

N = int(input())
AB = [tuple(map(int, input().split())) for _ in range(N)]
AB.sort(key=lambda t: t[1], reverse=True)
dp = [[10**18]*(N+1) for _ in range(N+1)]
dp[0][0] = 0

for i in range(N):
    A, B = AB[i]
    
    for j in range(N+1):
        dp[i+1][j] = min(dp[i+1][j], dp[i][j])
        
        if j+1<=N:
            dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j]+A+B*j)
    
ans = 10**18

for i in range(N+1):
    if i//2>=N-i:
        ans = min(ans, dp[N][i])
    
print(ans)