#include<bits/stdc++.h> using namespace std;

//double x1,y1,x2,y2; 要是在这里声明变量 OJ会报错 但是自己测试答案是正确的 也不知道为什么

double ans;

void juli(double x_1,double y_1,double x_2,double y_2) { ans=sqrt((x_1-x_2)(x_1-x_2) + (y_1-y_2)(y_1-y_2)); printf("%.2f\n",ans); }

int main() { double x1,y1,x2,y2;

while(scanf("%lf,%lf,%lf,%lf",&x1,&y1,&x2,&y2)!=EOF)
{
	juli(x1,y1,x2,y2);
}
return 0;

}