const vals = [1,2,3]
           
var lines = [];
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
reader.on('line', function(line) {
  lines.push(line);
});
reader.on('close', function() {
  	var ret = vals.filter(function(x) {
    	for (var i = 0; i<lines.length; i++) {
        	if (lines[i] == x)
              return false;
        }
      	return true;
    })[0]
    console.log(ret);
});