const fs = require('fs')
const readline = require('readline');

const readInterface = readline.createInterface({
    input: fs.createReadStream('input'),
    console: false
});

// [[x,y], [x,y], ...]
let seats = [];

function makeArray(n) {
  let ary = new Array(n);
  for(i=0; i<n; i++) {
    ary[i] = i;
  }

  return ary;
}

readInterface.on('line', function(line) {
  const rowSpec = line.substring(0, 7);
  const colSpec = line.substring(7, 10);

  let row = rowSpec.split('').reduce(function(range, char) {
    const half = Math.floor(range.length / 2);

    let r2 = range;
    switch(char) {
    case 'F': r2 = range.slice(0, half+1); break;
    case 'B': r2 = range.slice(half, range.length); break;
    };

    return r2;
  }, makeArray(128));
  
  let col = colSpec.split('').reduce(function(range, char) {
    const half = Math.floor(range.length / 2);

    let r2 = range;
    switch(char) {
    case 'L': r2 = range.slice(0, half+1); break;
    case 'R': r2 = range.slice(half,range.length); break;
    };

    return r2;
  }, makeArray(8));

  seats.push([col[0], row[0]]);
});

readInterface.on('close', function(line) {
  let seatIDs = new Set( seats.map((seat) => seat[1]*8 + seat[0]).sort((a,b) => a-b ) );

  for (x=0; x<8; x++) {
    for(y=0; y<128; y++) {
      let seatID = y*8+x;
      if (!seatIDs.has(seatID) && seatIDs.has(seatID-1) && seatIDs.has(seatID+1)) {
        console.log(seatID);
        break;
      }
    }
  }
});