[ Winner!! ] (614pts)

 : gs11008

Gold Medal List!! (over 420pts)

  : gs11008, gs12065, dijkstra, teram, gs10107, gs12059, gs12117

Silver Medal List (over 308pts)

  : issac, xxxxx, kk1401, seotos, gs12122, ainta, ryanchl, gs11135, ajou709

Bronze Medal List (over 218pts)

  : gs12047, jyj0312, gs12120, gs11098, gs11028, gs11117, gs11018, commaster0, gs12116, gs11103, woo960131, gs12115, mufflin, gs10102, gs12019

#include<stdio.h>
main()  	// by dijkstra
{
    int i,n;
    scanf("%d",&n);
    for(i=1;i*i<=n;i++);
    printf("%d",i-1);
}

#include <stdio.h>
#include <algorithm>

#define MAX 123456789		// by gs12065 (O(n^3) DP MAX n is 50)

int length, n, pos[55], dp[55][55];

int main(){
	scanf("%d%d", &length, &n);   

	int i, j, k;
	pos[0] = 0;
	for(i=1; i<=n; i++) scanf("%d", &pos[i]);
	pos[n+1] = length;

	std::sort(pos, pos+n+2);

	for(i=2; i<=n+1; i++){
		for(j=0; j+i<=n+1; j++){
			dp[j][j+i] = MAX;
			for(k=1; k<i; k++){
			   dp[j][j+i] = 
			      std::min(dp[j][j+i], pos[j+i]-pos[j]+dp[j][j+k]+dp[j+k][j+i]);
			}
		}
	}

	printf("%d\n", dp[0][n+1]);

	return 0;
}

#include<stdio.h>
int line[1010];
int ce[1010][1010];		// gs12117 (O(L^2) Memoization(DP) MAX L is 1000)
int cut(int s,int e){		
	if(ce[s][e]>0)return ce[s][e];
	int i,energy=999999999;
	for(i=s+1;i<e;i++){
		if(line[i]==1){
			if(energy>cut(s,i)+cut(i,e)){
				energy=cut(s,i)+cut(i,e);
			}
		}
	}
	if(energy==999999999)energy=0;
	ce[s][e]=energy+e-s;
	return ce[s][e];
}
int main(){
	int a,b,c,i;
	scanf("%d%d",&a,&b);
	for(i=0;i<b;i++){
		scanf("%d",&c);
		line[c]=1;
	}
	printf("%d",cut(0,a)-a);
}

#include <stdio.h>
#include <math.h>
#include <algorithm>
#define MIN(x,y) ((x)<(y)?(x):(y))

int n;
double ANS;		// by k5888200 (Divide & Conquer Solution)

struct X{
    double x,y;
}a[10005];

bool cmp_x(X aa, X bb){
    if(aa.x!=bb.x) return aa.x<bb.x;
    return aa.y<bb.y;
}
bool cmp_y(X aa, X bb){
    if(aa.y!=bb.y) return aa.y<bb.y;
    return aa.x<bb.x;
}

double len(X aa, X bb){return sqrt((aa.x-bb.x)*(aa.x-bb.x)+(aa.y-bb.y)*(aa.y-bb.y));}


double f(int left, int right){
    if(left==right) return ANS;
    if(left+1==right) return len(a[left],a[right]);

    double min1, min2, min, Min;
    int mid;
    mid=(left+right)>>1;

    min1=f(left,mid);
    printf("",min1);
    min2=f(mid+1,right);
    ANS=min=Min=MIN(min1,min2);

    int i,j,k,l;

    for(i=mid;i>left;i--) if(a[mid].x-min>a[i].x) break; left=i+1;
    for(i=mid;i<=right;i++) if(a[i].x>a[mid].x+min) break; right=i-1;


    std::sort(a+left,a+right+1,cmp_y);

    for(i=j=left;j<=right;j++){
        while(a[j+1].y<a[i].y+min && j+1<=right) j++;
        for(k=i;k<=j;k++){
            for(l=k+1;l<=j;l++){
                Min=MIN(Min,len(a[k],a[l]));
            }
        }

    }

    std::sort(a+left,a+right+1,cmp_x);

    return Min;
}
int main(){
    int i;
    scanf("%d",&n);
    for(i=1;i<=n;i++) scanf("%lf%lf",&a[i].x,&a[i].y);
    std::sort(a+1,a+1+n,cmp_x);
    ANS=len(a[1],a[2]);
    printf("%.2lf",f(1,n));
}

#include<stdio.h>
#include<memory.h>
int pre,n,qqq[510][2],x[510],chk[510],dap=1<<30,lll[510],z;
struct data{
	int a,b;				// by gs11008 (using IndexTree) almost Perfect
} indextree[1<<12];

int i,j,maxx;

int f(int a,int b){
	int M=0;
	while(a<b){
		if(~b&1){
			if(M<indextree[b].b)
				M=indextree[b].b;
			b--;
		}
		a>>=1,b>>=1;
	}
	if(a==b&&M<indextree[a].b)M=indextree[a].b;
	return M;
}
int main(){
	scanf("%d",&n);
	for(i=1;i<=n;i++)scanf("%d%d",qqq[i],qqq[i]+1);
	pre=x[0]=chk[1]=1;
	for(i=1;i<n;i++){
		if(chk[qqq[pre][0]]==0){
			chk[qqq[pre][0]]=1;
			x[i]=qqq[pre][0];
			pre=qqq[pre][0];
		}
		else if(chk[qqq[pre][1]]==0){
			chk[qqq[pre][1]]=1;
			x[i]=qqq[pre][1];
			pre=qqq[pre][1];
		}
		else break;
	}
	if(i!=n || (qqq[x[n-1]][0]!=1 && qqq[x[n-1]][1]!=1))return printf("-1");

	for(z=0;z<n;z++){
		memset(indextree,0,sizeof(indextree));
		for(i=0;i<n;i++)
			lll[i]=x[(i+z)%n];
		int p;
		for(p=1;p<=n;p*=2);
		for(i=0;i<n;i++){
			int t=p+lll[i]-1;
			indextree[t].a=1;
			indextree[t].b=f(p,t-1)+1;
			for(j=t;j>1;j>>=1){
				if(indextree[j>>1].a==0)indextree[j>>1]=indextree[j];
				else if(indextree[j>>1].b<indextree[j].b)indextree[j>>1]=indextree[j];
			}
		}
		if(n-indextree[1].b<dap)dap=n-indextree[1].b;
	}
	for(i=0;i<n/2;i++){
		int t=x[i];
		x[i]=x[n-i-1];
		x[n-i-1]=t;
	}
	for(z=0;z<n;z++){
		memset(indextree,0,sizeof(indextree));
		for(i=0;i<n;i++)
			lll[i]=x[(i+z)%n];
		int p;
		for(p=1;p<=n;p*=2);
		for(i=0;i<n;i++){
			int t=p+lll[i]-1;
			indextree[t].a=1;
			indextree[t].b=f(p,t-1)+1;
			for(j=t;j>1;j>>=1){
				if(indextree[j>>1].a==0)indextree[j>>1]=indextree[j];
				else if(indextree[j>>1].b<indextree[j].b)indextree[j>>1]=indextree[j];
			}
		}
		if(n-indextree[1].b<dap)dap=n-indextree[1].b;
	}
	printf("%d",dap);
}