#40009: 給應付課程的同胞
b558. 求數列第 n 項
| From: [114.25.208.4] |
發表日期
:
2024-04-20 11:38
#include <iostream>
using namespace std;
int main()
{
int n,x;
cin>>n;
x=1+((1+n-1)*(n-1))/2;
cout<<x;
return 0;
}
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