import std.stdio; // readln
import std.array; // split
import std.conv; // to

void main(){
	string[] s = split(readln());

	int a = to!int(s[0]);
	int b = to!int(s[1]);
	int c = to!int(s[2]);
	if(a == b) writeln(c);
	else if(a == c) writeln(b);
	else writeln(a);
}
