#include<stdio.h>

int main(void) {
	int P;
	int x, y, px, py, fx, fy;
	int L;

	scanf("%d", &P);
	while(P) {
		scanf("%d %d",&fx, &fy);
		P--;

		if(P == 0) {
			printf("The length of the fence will be 0 units.\n");
			scanf("%d", &P);
			continue;
		}
		
		px = fx; py = fy;
		L = 0;
		
		while(P) {
			scanf("%d %d", &x, &y);
			P--;
			if(x == px) {
				L += (py > y) ? py-y : y-py;
			} else {
				L += (px > x) ? px-x : x-px;
			}
			px = x;
			py = y;
		}
		
		if(x == fx) {
			L += (fy > y) ? fy - y : y - fy;
		} else {
			L += (fx > x) ? fx - x : x - fx;
		}
		
		printf("The length of the fence will be %d units.\n", L);
		
		scanf("%d", &P);
	}

	return 0;
}