#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(void){
	double x1;
	double x2;
	double y1;
	double y2;
	double res;
	printf("Donnez la coordonée 1 : \n");
	scanf("%lf", &x1);
	scanf("%lf", &y1);
	printf("Donnez la coordonée 2 : ");
	scanf("%lf", &x2);
	scanf("%lf", &y2);
	res= sqrt(pow((x1-x2),2)+pow((y1-y2),2));
	printf("%lf", res);
	return EXIT_SUCCESS;
}