题解 | 异或

#include <bits/stdc++.h>
using namespace std;
#define int long long
int gcd(int x,int y)
{
    return x==0?y:gcd(y%x,x);
}
void solve()
{
    int a,b,c,d;
    while(cin>>a)
    {
        cin>>b>>c>>d;
        int len1=b-a+1,len2=d-c+1;
        int sum=len1*len2;
        int res=0;
        if(c>=a&&d<=b)
        {
            res=len2;
        }
        else if(c<=a&&d>=b)
        {
            res=len1;
        }
        else if(c>=a)
        {
            if(c<=b)
            {
                res=(b-c+1);
            }
        }
        else
        {
            if(a<=d)
            {
                res=(d-a+1);
            }
        }

        if(res==0)
        {
            cout<<"0/1\n";
        }
        else 
        {
            int ans=gcd(res,sum);
            cout<<res/ans<<"/"<<sum/ans<<"\n";
        }
    }
}
signed main() 
{
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int t__=1;
    while(t__--)
    {
        solve();
    }
    return 0;
}