N = int(input())
lsAB = []
for i in range(N):
    A,B = map(int,input().split())
    lsAB.append([A,B])
lsAB.sort(key=lambda x:-x[1])
INF = float('INF')
if N%3==0:
    M = 2*(N//3)
elif N % 3 == 1:
    M = 2*(N//3)+1
else:
    M = 2*(N//3)+2
dp = [[INF]*(N) for i in range(M)]
for i in range(N):
    dp[0][i] = lsAB[i][0]
for i in range(1,M):
    rm = INF
    for j in range(N):
        dp[i][j]=rm+lsAB[j][0]+lsAB[j][1]*i
        rm = min(rm,dp[i-1][j])
print(min(dp[-1]))