const input = require('fs').readFileSync('/dev/stdin', 'utf8');
const n = Number(input);

const dp = [];
dp[0] = 1;
dp[1] = 1;
for (let i = 2; i <= n; i++) {
  dp[i] = dp[i - 1] + dp[i - 2];
}

console.log(dp[n]);

