import math

def main():
    X = int(input())
    Y = int(input())
    L = int(input())
    ans = 0
    if Y >= 0:
        ans = math.ceil(Y/L)
        if X != 0:
            ans += 1  # 右か左を向く
            ans += math.ceil(abs(X)/L)
    else: 
        ans += 1  # 右か左を向く
        ans += math.ceil(abs(X)/L)
        ans += 1 # 南をむく
        ans = math.ceil(Y/L)

    print(ans)


if __name__ == '__main__':
    main()