/*i,j,num,i,j,num..... 往复循环形成数列*/
int fun (int t)
{
int i=0,j=1,num=1; while(1)
{
num=i+j;
if(num>t) {return num; break;}
i=num+j;
if(i>t) {return i; break;}
j=i+num;
if(j>t) {return j; break;}
}
return -1;
}