C++ :

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <vector>
#include <utility>
#include <set>
//#define LOCAL
#define maxe 105
#define maxd 105
#define maxn 25
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
int n,E,D;
int dp[maxe][maxd],f[maxn][maxd];
int main(){
	#ifdef LOCAL
	freopen("sample.in","r",stdin);
	freopen("sample.out","w",stdout);
	#endif
	scanf("%d%d%d",&n,&E,&D);
	if(E < D){
		puts("0");
		return 0;
	}
	memset(dp,0x3f,sizeof(dp));
	for(int i=0;i<=E;i++) dp[i][0] = 0;
	for(int i=1;i<=E;i++){
		for(int j=1;j<=D;j++){
			for(int k=1;k <= j && k * k <= i;k++){
				dp[i][j] = min(dp[i][j],dp[i - k * k][j - k] + 1);
			}
		}
	}
	memset(f,0x3f,sizeof(f));
	f[0][0] = 0;
	for(int i=1;i<=n;i++){
		for(int j=0;j<=D;j++){
			int p = D - j;
			for(int k=0;k<=j;k++){
				f[i][j] = min(f[i][j],f[i - 1][j - k] + dp[E - p][k]);
			}
		}
	}
	printf("%d\n",f[n][D]);
	return 0;
}