Use 1-6 random generator to generate 1-7 random number

Use 1-6 random generator to generate 1-7 random number

int foo()
{
do
{
int x=rand6-1;//0~5
int y=rand6-1;
}
while((x*6+y)==35); //0~34 is valid
return (x*6+y)%7+1;//1~7
}