C语言 Sixth Grade Math

#include<stdio.h>
int hcf(long a,long b)
{
int r = 0;
while(b != 0)
{r = a % b; a = b; b = r;}
return a;
}
int main()
{
long d = 1,a,b,c,c1,t; //d应在循环外赋初值，在循环内则总为1