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) :
    dpR = [maxCost if i != 0 else R[0]]
    dpG = [maxCost if i != 1 else G[0]]
    dpB = [maxCost if i != 2 else B[0]]
    
    for n in range(1, N) :
        r, g, b = R[n], G[n], B[n]
        dpR.append(r + min(dpG[n-1], dpB[n-1]))
        dpG.append(g + min(dpR[n-1], dpB[n-1]))
        dpB.append(b + min(dpR[n-1], dpG[n-1]))
    
    if i==0 :
        result.append(min(dpG[N-1], dpB[N-1]))
    elif i==1 :
        result.append(min(dpR[N-1], dpB[N-1]))
    else :
        result.append(min(dpR[N-1], dpG[N-1]))

print(min(result))