C++(씨쁠쁠)(cplusplus)-백준(baekjoon)(BaekJoon)코딩 2193번:이친수 답

#include<iostream>
int main(){
    unsigned long long n,a=1,b=1,c=1;
    std::cin>>n;
    for(int i=2;i<n;i++)
    {c=a+b;a=b;b=c;}
    printf("%llu",c);}