import sys

input = sys.stdin.readline

maxCost = 1000
N = int(input())
R = []
G = []
B = []

for _ in range(N) :
    r, g, b = map(int, input().split())
    R.append(r)
    G.append(g)
    B.append(b)

result = []

for i in range(3) :
    prevR = maxCost if i != 0 else R[0]
    prevG = maxCost if i != 1 else G[0]
    prevB = maxCost if i != 2 else B[0]
    
    for n in range(1, N) :
        r, g, b = R[n], G[n], B[n]
        curR = r + min(prevG, prevB)
        curG = g + min(prevR, prevB)
        curB = b + min(prevR, prevG)
        
        prevR, prevG, prevB = curR, curG, curB
    
    if i==0 :
        result.append(min(prevG, prevB))
    elif i==1 :
        result.append(min(prevR, prevB))
    else :
        result.append(min(prevR, prevG))

print(min(result))