N = int(input())
C = [0] * N
D = [0] * N
for i in range(N):
    C[i], D[i] = map(int, input().split())

INF = pow(10, 12)
dp = [INF] * (N+1)
dp[0] = 0

for i in range(N):
    dp[i+1] = min(dp[i+1], dp[i] + C[i] * 2)
    if i >= 1:
        dp[i+1] = min(dp[i+1], sum(C[:i+1]) + min(C[:i+1]) + sum(D[:i+1]) - D[0])
    for j in range(i):
        dp[i+1] = min(dp[i+1], dp[j] + sum(C[j:i+1]) + min(C[j:i+1]) + sum(D[j:i+1]) - D[j])


print(dp[N])