#include using namespace std; typedef signed long long ll; #undef _P #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x>N>>M; ll g=__gcd(N,M); N/=g; M/=g; if(N%M==0) { N/=M; while(N%10==0) N/=10; return _P("%lld\n",N%10); } N%=M; while(M%2==0) M2++, M/=2; while(M%5==0) M5++, M/=5; if(M!=1) return _P("-1\n"); while(M2M5) { M5++; N*=5; while(N%10==0) N/=10; } _P("%lld\n",N%10); } int main(int argc,char** argv){ string s;int i; if(argc==1) ios::sync_with_stdio(false); FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin); solve(); return 0; }