求教大神为什么只有80(牛逼的是我错了第二个点)

#include<cstdio>
#include<algorithm>
using namespace std;
void common (int x,int y);
int pn[3];
int main()
{
    for (int i=0;i<=2;++i)
     scanf("%d",&pn[i]);
    sort(pn,pn+3);
    common(pn[0],pn[2]);
    printf("%d/%d",pn[0],pn[2]);
    return 0;
}
void common (int x,int y)
{
    int m=x,n=y,r;
    do
    {
        r=m%n;
        m=n;
        n=r;
    }while (r!=0);
    x/=m;
    y/=m;
}