代码附有注释，已有缩进，直接复制即可

x1,y1=map(float,input().split()) x2,y2=map(float,input().split()) x3,y3=map(float,input().split()) a1=((x2-x1)**2+(y2-y1)**2)**0.5 a2=((x3-x1)**2+(y3-y1)**2)**0.5 a3=((x3-x2)**2+(y3-y2)**2)**0.5 print("%.2f"%(a1+a2+a3))