求助，80分

#include <stdio.h>

int main()
{
    int n;
    scanf("%d",&n);
    int c = 0;
    double xn = (double)n;
    if(n <= 1)
    {
        puts("0");
        return 0;
    }
    while(xn > 1)
    {
        xn /= 2;
        c++;
    }
    printf("%d\n",c);
    
}