PBCDEM – SPOJ

using namespace std;
#include<bits/stdc++.h>
#define FOR(i, a, b) for (int i = a; i < b; i++)
#define FORE(i, a, b) for (int i = a; i <= b; i++)
#define FORD(i, a, b) for (int i = a; i >= b; i--)
const int MAXN = 5001;
const int INF = 1e9 + 7;
 
string f[5001][101];
int n;
 
string operator +(string a, string b)
{
    FORE(i, a.length(), b.length() - 1) a = '0' + a;
    FORE(i, b.length(), a.length() - 1) b = '0' + b;
    string c = a;
    int nho = 0;
    FORD(i, a.length() - 1, 0){
        int tmp = (a[i] - '0') + (b[i] - '0') + nho;
        c[i] = (tmp % 10 + '0');
        nho = tmp / 10;
    }
    if (nho) c = '1' + c;
    return c;
}
 
int main()
{
    ios::sync_with_stdio(false); cin.tie(0);
    cin >> n;
    //cout<<"wtf"<<endl;
    int cur = 0, prev = 1;
    FORE(i, 0, n + 2) FORE(j, 0, 100) f[i][j] = '0';
    f[0][0] = "1";
    FORE(i, 1, n) FORE(j, 1, trunc(sqrt(i*2)) + 1) if (1LL * j * (j + 1) <= 2 * i) f[i][j] = f[i - j][j] + f[i - j][j - 1];
    string ans = "0";
    FORE(j, 2, trunc(sqrt(n*2)) + 1) ans = ans + f[n][j];
    cout<<ans;
	return 0;
}