#include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define FOR(I,A,B) for(int I = (A); I < (B); ++I) typedef long long ll; int main(){ int x1,y1,x2,y2; cin >> x1 >> y1 >> x2 >> y2; int xx = abs(x1 - x2); int yy = abs(y1 - y2); cout << (xx + 1) / 2 + (yy + 1) / 2 << endl; return 0; }