#include <cstdio>

const int MAX = 100;

int main()
{
	int test, t, i, arr[MAX], co, pro;
	for(scanf("%d", &test); test--; ){
		scanf("%d%d", &t, arr);
		if(t == 1){
			printf("%d\n", arr[0]);
			continue;
		}
		if(arr[0] == 1){
			puts("0");
			continue;
		}

		co = 0;
		for(i = 1; i < MAX; ++i){
			pro = arr[i-1] * t + co;
			arr[i] = pro % 10;
			co = pro / 10;
			if(arr[i] != 0 && arr[i]*t + co == arr[0]) break;
		}
		if(i == MAX) puts("0");
		else{
			for(; i >= 0; --i) printf("%d", arr[i]);
			puts("");
		}
	}
	return 0;	
}