function main (s) {
	s=s.split(" ");
    for(var i=0;i<3;i++)s[i]=parseInt(s[i]);
	if(s[0]==s[1])console.log(s[2]);
	else if(s[0]==s[2])console.log(s[1]);
	else console.log(s[0]);
}
 
main(require('fs').readFileSync('/dev/stdin', 'utf8'));