请问错误是怎么回事

#include<iostream>
#include <iomanip>
#include <math.h>
using namespace std;
class sanjiaoxing
{
private:
    double x,y,z;
public:
    void shuru(double a,double b,double c);
    void mianji();
    void chouchang();
};
void sanjiaoxing::shuru(double a,double b,double c)
{
    x=a;
    y=b;
    z=c;
}
void sanjiaoxing::chouchang()
{
    cout<<x+y+z<<endl;
}
void sanjiaoxing::mianji()
{
    int d,e,f,g;
    d=1/(2*(x+y+z));
    e=sqrt(d*(d-x)*(d-y)*(d-z));
    cout<<g<<endl;
}
void main()
{
    sanjiaoxing 1;//error C2143: syntax error : missing ';' before 'constant'
    int a,b,c,i;
    cin>>a>>b>>c;
    1.shuru(a,b,c);//error C2059: syntax error : 'bad suffix on number'error C2146: syntax error : missing ';' before identifier 'shuru'还有个shuru未定义
    1.chouchang();//和上行差不多的错误提示
    1.mianji();//和上行差不多的错误提示
}