AE00 SPOJ

AE00.cpp

// contest : http://www.spoj.com/problems/AE00/
// author  : Nguyen Minh Tuan (ititorit)
// language: C/C++

#include <bits/stdc++.h>

#define _for(i,a,b) for(int i=(a),_b_=(b),_d_=(a<b?1:-1);i!=_b_;i+=_d_)
#define FOR(i,a,b) for(int i = a; i <= b; i++)
#define _it(i,v) for (typeof((v).begin()) i = (v).begin(); i != (v).end(); ++i)
#define _all(v) v.begin(), v.end()

#define DEBUG(x) { cout << #x << " = " << x << endl; }
#define sqr(x) ((x)*(x))
 
using namespace std;
typedef long long ll;
typedef unsigned long long ull;

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    #ifndef ONLINE_JUDGE
    freopen("INPUT.inp", "r", stdin);
    #endif

    // solution starts...

    int a;
    cin >> a;
    int ans = 0;
    FOR(i,1,sqrt(a)) { ans += a/i -i + 1; }
    cout << ans << endl;

    // solution ends...

    return 0;
}