import java.util.*;
public class g {
	Scanner in=new Scanner(System.in);
	public static void main(String[] args) {
		new g().go();
	}
	private void go() {
		int n=in.nextInt(),d=in.nextInt();
		double l=in.nextDouble()*1000/d;
		int[][] p=new int[n][2];
		for(int i=0;i<n;i++){
			p[i][0]=in.nextInt();
			p[i][1]=in.nextInt();
		}
		int[] c=new int[2];
		for(int i=0;i<n;i++){//find bottom left and top right
			if(p[i][1]==0&&p[(i+1)%n][1]==0)c[0]=i;
			if(p[i][1]!=0&&p[(i+1)%n][1]==p[i][1])c[1]=i;
		}
		int curl=c[0],curr=(c[0]+1)%n;
		double[] base={p[curl][0],p[curr][0],p[curr][1]};//x0,x1,h of current water level
		curl=(curl-1+n)%n;//candidate next fill points
		curr=(curr+1)%n;
		while(l!=0&&curl!=c[1]){//stop when we're out of water or we've reached the top
			if(p[curl][1]<p[curr][1]){
				double h=p[curl][1]-base[2];
				double nextr=base[1]+(p[curr][0]-base[1])*h/(p[curr][1]-base[2]);
				double a=h*(nextr-p[curl][0]+base[1]-base[0])/2;
				if(a<l){
					l-=a;
					base[0]=p[curl][0];
					base[1]=nextr;
					base[2]=base[2]+h;
					curl=(curl-1+n)%n;
				} else {
					base[2]=base[2]+quad(l,base[1]-base[0],h,nextr-base[1],p[curl][0]-base[0]);
					l=0;
				}
			} else if(p[curl][1]>p[curr][1]){
				double h=p[curr][1]-base[2];
				double nextl=base[0]+(p[curl][0]-base[0])*h/(p[curl][1]-base[2]);
				double a=h*(p[curr][0]-nextl+base[1]-base[0])/2;
				if(a<l){
					l-=a;
					base[0]=nextl;
					base[1]=p[curr][0];
					base[2]=base[2]+h;
					curr=(curr+1)%n;
				} else {
					base[2]=base[2]+quad(l,base[1]-base[0],h,p[curr][0]-base[1],nextl-base[0]);
					l=0;
				}
			} else {
				double a=(p[curr][1]-base[2])*(p[curr][0]-p[curl][0]+base[1]-base[0])/2;
				if(a<l){
					l-=a;
					base[0]=p[curl][0];
					base[1]=p[curr][0];
					base[2]=p[curr][1];
					curl=(curl-1+n)%n;
					curr=(curr+1)%n;
				} else {
					base[2]=base[2]+quad(l,base[1]-base[0],p[curr][1]-base[2],p[curr][0]-base[1],p[curl][0]-base[0]);
					l=0;
				}
			}
		}
		System.out.printf("%.2f\n",base[2]);
	}
	private double quad(double area, double bottom_base, double height, double right_offset, double left_offset) {//given a trapezoid and an area, computes how high up to go
		if(right_offset == left_offset)return height*area/((bottom_base+bottom_base+right_offset-left_offset)/2*height);//actually a parallelogram
		double a=right_offset/height-left_offset/height;
		double b=2*bottom_base;
		double c=-2*area;
		double z1=(-1*b+Math.sqrt(b*b-4*a*c))/2/a;
		double z2=(-1*b-Math.sqrt(b*b-4*a*c))/2/a;
		return z1;
	}
}