已知三角形的三条中线长度求面积

题意：给出三角形的三条中线长度求面积。

#include <iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>using namespace std;int main(){    double n,m,p;    while(cin>>n>>m>>p)    {        if((m+n+p)*(m+p-n)*(m+n-p)*(n+p-m)<=0||m<=0||n<=0||p<=0||m+p<=n||n+p<=m||m+n<=p) puts("-1.000");        else printf("%.3lf\n",sqrt((m+n+p)*(m+p-n)*(m+n-p)*(n+p-m))/3.0);    }    return 0;}