var lines = require("fs").readFileSync("input.txt").toString().split("\n").filter((a)=>(a));
var top = lines[0].split(" ")[0];
var oldtop = "";
while(oldtop != top){
	oldtop = top;
	for(var line of lines){
		console.log(line);
		if(line.indexOf("->") != -1){
			if(line.split(" -> ")[1].split(", ").indexOf(top) != -1){
				top = line.split(" ")[0];
			}
		}
	}
}
console.log(top);