UVA11636 - Hello World!

#include <stdio.h>#include <stdlib.h>#include<math.h>int powr(int a,int n){    int p=1;    while(n--)        p*=a;    return p;}int main(){   int a,b,u=0;   scanf("%d",&a);   while(~scanf("%d",&b))   {        int n=abs(log2(a)+1);        if(powr(2,n-1)==a)            printf("Case %d: %d\n",++u,n-1);        else            printf("Case %d: %d\n",++u,n);        a=b;   }   return 0;}