#include<stdio.h>
 int main(void)
 {
	int kannsenn[100];
	int cnt,m,n,p,a,b,i,j,k,same;
	while(1){
		scanf("%d",&m);
		scanf("%d",&n);
		scanf("%d",&p);
		kannsenn[0] = p;
		cnt = 1;
		
		if(m == 0 && n == 0 && p == 0){
			break;
		}
		
		for(i = 0;i < n;i++){
			scanf("%d",&a);
			scanf("%d",&b);
			same = 0;
 
			for(j = 0;j < cnt;j++){
				if(kannsenn[j] == a){
					for(k = 0;k < cnt;k++){
						if(b == kannsenn[k]){
							same = 1;
							break;
						}
					}
					if(same == 1){
						break;
					}
					else{
					kannsenn[cnt] = b;
					cnt++;
					break;
					}
				 }
				 else{
					if(kannsenn[j] == b){
						for(k = 0;k < cnt;k++){
							if(a == kannsenn[k]){
								same = 1;
								break;
							}
						}
						if(same == 1){
							break;
						}
						else{
							kannsenn[cnt] = a;
							cnt++;
							break;
						}
						}
					}
				}
		}
		printf("%d\n",cnt);
	}
	
	return 0;
 }