#include<bits/stdc++.h>
using namespace std;
#define lli long long int
#define inf 1000000000
#define pb push_back
#define mp make_pair
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
#define yoi cout<<"yo"<<endl;
#define debug(x) cerr << #x << " is " << x << endl;
#define all(x) x.begin(),x.end()
const int mod=1e9+7;
int main(){
IOS;
lli p,q,r,s,i,j;
cin>>p>>q>>r>>s;
lli ans=0;
for(i=p;i<=q;i++){
    for(j=r;j<=s;j++){
        lli x=max(i,j);
        lli y=min(i,j);
        while(x&&y){
            ans+=(x/y);
            x=x%y;
            swap(x,y);
        }
    }
}
cout<<ans;
}
 

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