https://www.acmicpc.net/problem/2193
let fs = require('fs');
let input = Number(fs.readFileSync('/dev/stdin').toString());
function answer(n) {
let a = 1;
let b = 1;
for(let i=3; i<=n; i++) {
let tmp = BigInt(a)+BigInt(b);
a = b;
b = tmp;
}
return b.toString();
}
console.log(answer(input));
오버플로우 나는 것 같길래 BigInt 처음 써봤다