Program to implement Extended Euclidean algorithm

This version is for RSA public-key encryption method.
e*d mod z =1

it takes the value of e or d and returns the value of  d or e respectively.

#include <stdio.h>
#include <string.h>
int z,ed;
int ee_algo(int x1,int x2,int x3,int y1,int y2,int y3)
{ int q=x3/y3;
     int tx1=y1;
     int tx2=y2;
     int tx3=y3;
     y1=x1-q*y1;
     y2=x2-q*y2;
     y3=x3-q*y3;
   
    if(y3==1)
    { if(y2>0)
       return y2;
       else return y2+z;

    }
  else
  {   x1=tx1;
     x2=tx2;
     x3=tx3;
       
      return ee_algo(x1,x2,x3,y1,y2,y3);
  }

}
main()
{
    z=2400;

  ed=29;
   printf("%d",ee_algo(1,0,z,0,1,ed));
}