http://acm.hdu.edu.cn/showproblem.php?pid=2504
#include<stdio.h> int gcd(int a,int b) { int r=a%b; while(r) { a=b; b=r; r=a%b; } return b; } int main() { int t,a,b,c; scanf("%d",&t); while(t--) { scanf("%d%d",&a,&b); c=2*b; while(gcd(a,c)!=b) c+=b; printf("%d ",c); } return 0; }