Не запускается программа

Пытаюсь нарисовать треугольник, но что то идет не так.

#include <iostream>
#include <graphics.h>
struct Pnt{
    int x,y;
};
class Trn{
    public:
        Pnt a,b,c;
        Trn(Pnt,Pnt,Pnt);
        void show();
};
Trn::Trn(Pnt A,Pnt B,Pnt C){
    a=A;
    b=B;
    c=C;
};
void Trn::show(){
    int Poly[8]={a.x,a.y,b.x,b.y,c.x,c.y};
    drawpoly(4,Poly);
};
int main(){
    int gd=DETECT,gm;
    initgraph(0,0,"");
    Pnt a,b,c;
    a.x=100;
    a.y=100;
    b.x=190;
    b.y=100;
    c.x=100;
    c.y=190;
    Trn trn1(a,b,c);
    trn1.show();
    system("PAUSE");
    closegraph();
};

C:\Users\zxcvbnm\Documents\prj1\main.cpp    In function 'int main()':
29  18  C:\Users\zxcvbnm\Documents\prj1\main.cpp    [Warning] deprecated conversion from string constant to 'char*' [-Wwrite-strings]
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/lib/libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/lib\libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../../../lib/libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../../../lib\libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../../libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../..\libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/lib/libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../../../lib/libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    skipping incompatible C:/Program Files (x86)/Dev-Cpp/MinGW64/bin/../lib/gcc/x86_64-w64-mingw32/4.9.2/../../../libbgi.a when searching for -lbgi
C:\Program Files (x86)\Dev-Cpp\MinGW64\x86_64-w64-mingw32\bin\ld.exe    cannot find -lbgi
C:\Users\zxcvbnm\Documents\prj1\collect2.exe    [Error] ld returned 1 exit status
25      C:\Users\zxcvbnm\Documents\prj1\Makefile.win    recipe for target 'prj1.exe' failed