POJ ( acm.pku.edu.cn ) 3673

#include <iostream>
using namespace std;
unsigned __int64 mul(char* a,char*b){
   unsigned __int64 r=0;
   for(;*a;++a) {
       if(*a=='0')continue;
       for(char* c=b;*c;++c) {
           r+=(*a-'0')*(*c-'0');
       }
   }
   return r;
}
int main()
{
   for(char a[16],b[16];cin>>a>>b;cout<<mul(a,b)<<endl);
   return 0;
}