#include<stdio.h>
#include<math.h>
#include<string.h>
#include<stdlib.h>
#include<ctype.h>

int main(){
    int x,y,z;
    scanf("%d%d%d",&x,&y,&z);
    if(abs(x-y)==z)printf("%d",z);
    else if(abs(x-z)==y) printf("%d",y);
    else printf("%d",x);
    return 0;
}