来源:HDU 1002
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
int main(){
long long n;
while(scanf("%lld",&n)!=EOF){
cout<<n*(n+1)/2<<endl<<endl;
}
return 0;
}
来源:HDU 1002
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
int main(){
long long n;
while(scanf("%lld",&n)!=EOF){
cout<<n*(n+1)/2<<endl<<endl;
}
return 0;
}