为什么开O2优化就TLE，关了就AC

#include <bits/stdc++.h>
using namespace std;
int dis(){
    float a,b,c,d,e,f;
    float m,n,p,q;
    cin>>a>>b;
    cin>>c>>d;
    cin>>e>>f;
    m = sqrt((e - a) * (e - a) + (f - b) * (f - b));
    n = sqrt((c - a) * (c - a) + (d - b) * (d - b));
    p = sqrt((e - c) * (e - c) + (f - d) * (f - d));
    q = float(m + n + p);
    printf("%.2f", q);
}
int main(){
    dis();
    return 0;
}