1:
#include <iostream>
using namespace std;
int main() {
int n, suma = 0;
cin >> n;
for (int i = 1; i<=n; i++) {
suma += i;
}
cout << suma;
return 0;
}
2:
#include <iostream>
using namespace std;
int main() {
int n, suma = 0, i = 0;
cin >> n;
while(i<(n+1)) {
suma += i;
i++;
}
cout << suma;
return 0;
}