C program to find the equation of straight line passing through the point (x1,y1) and (x2,y2)

#include<stdio.h>
#include<conio.h>
int g,l;
int gcd(int i,int j,int k)
{
int p;
for(p=1;p<=l;p++)
{
if(i%p==0&&j%p==0&&k%p==0)
g=p;
}
return g;
}
void main()
{
int x1,y1,x2,y2,a,b,c;
puts("Enter the first co-ordinate");
printf("x1=");
scanf("%d",&x1);
printf("y1=");
scanf("%d",&y1);
puts("Enter the second co-ordinate");
printf("x2=");
scanf("%d",&x2);;
printf("y2=");
scanf("%d",&y2);
a=y2-y1;
b=x1-x2;
c=(y1*(x2-x1))-(x1*(y2-y1));
l=a>b?(a>c?a:c):(b>c?b:c);
g=gcd(a,b,c);
if(a!=0)
printf("%dx",a/g);
if(b!=0)
b<0?printf("%dy",b/g):printf("+%dy",b/g);
if(c!=0)
c<0?printf("%d=0",c/g):printf("+%d=0",c/g);
}