求大佬看一下，哪里有问题80分最后一个不对

#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
float dis(int a, int b, int c, int d);
int main() {
	int x1, x2, y1, y2, x3, y3;
	double a,b,c,sum;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	a = dis(x1, y1, x2, y2);
	b = dis(x1, y1, x3, y3);
	c = dis(x2, y2, x3, y3);
	sum=a + b + c;
	cout << fixed << setprecision(2) << sum;
}

float dis(int a, int b,int c,int d) {
	float distant;
	distant = sqrt((a - c) * (a - c) + (b - d) * (b - d));
		return distant;
}