#include <stdio.h>

int main() 
{
    int a=0,b=0,c=0,d=0;
    scanf("%d %d %d %d",&a,&b,&c,&d);
    int x=a>b?a:b;
    int y=c>d?c:d;
    printf("%d",x>y?x:y);
    return 0;
}