C program to find GCD (Greatest Common Divisor) of two numbers

#include<stdio.h>
#include<conio.h>
long int gcd(long int a, long int b)
{
long int c;
if(a<b)
{
c=a;
a=b;
b=c;
}
if(a%b==0)
return b;
else
return gcd(b,a%b);
}
void main()
{
long int x,y,z;
scanf("%ld%ld",&x,&y);
z=gcd(x,y);
printf("gcd is %ld",z);
}