screen 尺寸为a:b
video 尺寸为 c:d
如果a == c 则 面积比为 cd/ab=ad/cb （ad < cb）
如果b == d 则 面积比为 cd/ab=cb/ad (cb < ad)
如果不相等时
如果a/b > c/d，则ad/bd > cb/db 则(ad > cb)
screen尺寸可为 ad：bd， video的尺寸可为 cb:db
面积比为：cb*db/ad*bd = cb/ad (ad > cb)
如果a/b < c/d，则ac/bc < ca/da 则(ad < cb)
screen尺寸可为 ac：bc， video的尺寸可为 ca:da
面积比为：ca*da/ac*bc = ad/cb (ad < cb)
综合得面积比为min(ad,cb)/max(ad,cb)
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int gcd(int n, int m){
while(m){
int t = n%m;
n = m;
m = t;
}
return n;
}
int main(){
int a,b,c,d;
cin >> a >> b >> c >> d;
int video = c*b, screen = a*d;
if(video > screen) swap(screen,video);
int k = gcd(screen,video);
video/=k;screen/=k;
cout<<screen-video<<"/"<<screen<<endl;
}