#include #include #include using namespace std; using namespace atcoder; using mint = modint998244353; #define rep(i,n) for (int i = 0; i < (n); ++i) #define Inf32 1000000000 #define Inf64 1000000000000000001LL int main(){ long long a,b,c,d; cin>>a>>b>>c>>d; long long g = gcd(abs(a),abs(b)); g = gcd(g,abs(c)); g = gcd(g,abs(d)); long long t = a * d - b * c; t = abs(t); long long x; if(g==0)x = 0; else x = t / g; cout<