#include #include #include int main(){ int x,y,w,h; int a,b,c,d; int s1,s2; scanf("%d %d %d %d",&x,&y,&w,&h); a=h-y; b=x; c=y; d=w-x; if(a>b){ s1=b; } else { s1=a; } if(c>d){ s2=d; } else{ s2=c; } if(s1>s2){ printf("%d",s2); } else{ printf("%d",s1); }}