C++ :

#include<stdio.h>
#include<stdlib.h>
 
#define eps 1e-8
#define zero(x) (((x)>0?(x):(-x))<eps)
 
struct point
{
    double x,y;
}p[100001],convex[100001],p1,p2,minp;
 
double xmult(point p1,point p2,point p0)
{
    return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
}
 
int graham_cp(const void* a,const void* b)
{
    double ret=xmult(*((point*)a),*((point*)b),p1);
    return zero(ret)?(xmult(*((point*)a),*((point*)b),p2)>0?1:-1):(ret>0?1:-1);
}
 
void _graham(int n,point* p,int& s,point* ch)
{
    int i,k=0;
    for(p1=p2=p[0],i=1;i<n;p2.x+=p[i].x,p2.y+=p[i].y,i++)
        if(p1.y-p[i].y>eps||(zero(p1.y-p[i].y)&&p1.x>p[i].x))
            p1=p[k=i];
        p2.x/=n;
        p2.y/=n;
        p[k]=p[0];
        p[0]=p1;
        qsort(p+1,n-1,sizeof(point),graham_cp);
        for(ch[0]=p[0],ch[1]=p[1],ch[2]=p[2],s=i=3;i<n;ch[s++]=p[i++])
            for(;s>2&&xmult(ch[s-2],p[i],ch[s-1])<-eps;s--);
}
 
int gramham(int n,point* p,point* convex,int maxsize,int dir)
{
    point* temp=new point[n];
    int s,i;
    _graham(n,p,s,temp);
    for(convex[0]=temp[0],n=1,i=(dir?1:(s-1));dir?(i<s):i;i+=(dir?1:-1))
        if(maxsize||!zero(xmult(temp[i-1],temp[i],temp[(i+1)%s])))
            convex[n++]=temp[i];
    delete []temp;
    return n;
}
 
int main()
{
    int n,i=0,pos;
    double x,y;
    char s[2];
    scanf("%d",&n);
    while(n--)
    {
        scanf("%lf%lf%s",&x,&y,s);
        if(s[0]=='Y')
        {
            p[i].x=x;
            p[i++].y=y;
        }
    }
    n=gramham(i,p,convex,1,0);
    printf("%d\n",n);
    minp=convex[0];
    pos=0;
    for(i=1;i<n;i++)
    {
        if(convex[i].x<minp.x)
        {
            pos=i;
            minp=convex[i];
        }
        else if(convex[i].x==minp.x)
        {
            if(convex[i].y<minp.y)
            {
                pos=i;
                minp=convex[i];
            }
        }
    }
    for(i=pos;i<n;i++)
        printf("%.f %.f\n",convex[i].x,convex[i].y);
    for(i=0;i<pos;i++)
        printf("%.f %.f\n",convex[i].x,convex[i].y);
    return 0;
}