Даны координаты вершин много угольника

// Периметр многоугольника.cpp: определяет точку входа для консольного приложения.
//
 
#include "stdafx.h"
#include "iostream"
#include <math.h>
#include <cmath>
using namespace std;
 
float t_f( float  x1, float y1, float x2, float y2) 
 {float rez;
 
     rez= sqrt ( pow( x2 - x1, 2 ) + pow ( y2 - y1 , 2));
     return rez;
    }
int _tmain(int argc, _TCHAR* argv[])
{ float P, a, b, c, d, e, f, g, h, k, m, x1, y1, x2, y2, x3, y3, x4, y4, x5, y5, x6, y6, x7, y7, x8, y8, x9, y9, x10, y10;
    
    cout<<"Vvedite x1, y1"<<endl; cin>>x1>>y1; cout<<"\n";//1
    cout<<"Vvedite x2, y2"<<endl; cin>>x2>>y2; cout<<"\n";//2
    cout<<"Vvedite x3, y3"<<endl; cin>>x3>>y3; cout<<"\n";//3
    cout<<"Vvedite x4, y4"<<endl; cin>>x4>>y4; cout<<"\n";//4
    cout<<"Vvedite x5, y5"<<endl; cin>>x5>>y5; cout<<"\n";//5
    cout<<"Vvedite x6, y6"<<endl; cin>>x6>>y6; cout<<"\n";//6
    cout<<"Vvedite x7, y7"<<endl; cin>>x7>>y7; cout<<"\n";//7
    cout<<"Vvedite x8, y8"<<endl; cin>>x8>>y8; cout<<"\n";//8
    cout<<"Vvedite x9, y9"<<endl; cin>>x9>>y9; cout<<"\n";//9
    cout<<"Vvedite x10, y10"<<endl; cin>>x10>>y10; cout<<"\n";//10
 
    a = t_f(x1, y1, x2, y2);//расстояние от x1
    b = t_f(x2, y2, x3, y3);//2
    c = t_f(x3, y3, x4, y4);//3
    d = t_f(x4, y4, x5, y5);//4
    e = t_f(x5, y5, x6, y6);//5
    f = t_f(x6, y6, x7, y7);//6
    g = t_f(x7, y7, x8, y8);//7
    h = t_f(x8, y8, x9, y9);//8
    k = t_f(x9, y9, x10, y10);//9
    m = t_f(x10, y10, x1, y1);//10
    P = a + b + c + d + e + f + g + h + k + m;
    cout<<"perimetr P="<<P<<"\n";
    
    return 0;
}