Te folosesti de formula de la mate.
Sn = [tex]\frac{(a_{n}+a_{1})n}{2}[/tex]
Unde n = [tex]\frac{(a_{n}-a_{1})}{r} + 1[/tex]
Programul:
#include <iostream>
using namespace std;
long long int n,i,S;
int main() {
cin>>n;
S=(n-(n/2))*(n-(n/2));
cout<<S;
return 0;
}
