if let N = Int(readLine() ?? "") {
    var RGB: [[Int]] = []
    for _ in 0..<N {
        guard let input = readLine(),
              let rgb = input.split(separator: " ").compactMap({Int($0)}) as? [Int],
              rgb.count == 3 else { break }
        
        RGB.append(rgb)
    }
    
    let maxCost = 1001
    var result = Int.max
    
    for i in 1...3 {
        var prevR = i != 1 ? maxCost : RGB[0][0]
        var prevG = i != 2 ? maxCost : RGB[0][1]
        var prevB = i != 3 ? maxCost : RGB[0][2]
        
        for j in 1..<N {
            let currentR = RGB[j][0] + min(prevG, prevB)
            let currentG = RGB[j][1] + min(prevR, prevB)
            let currentB = RGB[j][2] + min(prevG, prevR)
            
            (prevR, prevG, prevB) = (currentR, currentG, currentB)
        }
        
        if i==1 {
            result = min(result, prevG, prevB)
        }
        else if i==2 {
            result = min(result, prevR, prevB)
        }
        else {
            result = min(result, prevG, prevR)
        }
    }
    
    print(result)
}