var components = require("fs").readFileSync("input.txt").toString().split("\n").filter(a=>(a)).map(a=>(a.split("/").map(b=>(parseInt(b)))));
var finalBridges = [];
function getLongerChains(state){
	var additions = components.filter(a=>(state.components.indexOf(a) == -1)).filter(a=>(a[0] == state.end || a[1] == state.end));
	if(additions.length == 0){
		finalBridges.push(state.components)
	}
	else{
		additions.forEach(a=>{
			var newState = {
				components: state.components.slice(),
				end: a.filter((b,i)=>(i!=a.indexOf(state.end)))[0]
			}
			newState.components.push(a);
			//console.log(newState);
			getLongerChains(newState);
		});
	}
}
getLongerChains({
	components: [],
	end: 0
});
var bridgeLengths = finalBridges.map(bridge=>(bridge.map(a=>(a[0] + a[1])).reduce((a,b)=>(a+b))));
console.log(bridgeLengths.reduce((g, b)=>((b>g || g==null) ? b : g),null));