老师出的期末作业，编了几个小时，还程序出错，求大神解答.....

#include<stdio.h>
int b1;
int main()
{
int great(int a,int b);
int small(int a,int b);
int x,y,z,c;
printf("please enter two number:\n");
scanf("%d %d",x,y);
z=great(x,y);
c=small(x,y);
printf("最小公倍数是:%d\n",z);
printf("最大公约数是:%d\n",c);
return 0;
} int great(int a,int b)
{
int a1,e;
if(a>0&&b>0)
{ a1=a;
b1=b;
e=a1%b1;
while(e!=0)
{
a1=b1;
b1=e;
e=a1%b1;
}
}
return(b1);
} int small(int a,int b)
{int f;
f=a*b/b1;
return (f);
}