#include<stdio.h>
#include<math.h>

int main()
{
    int n,k,i=1,s=1,t=0,temp=0;
    scanf("%d %d",&n,&k);

    while(i<k)
    {
        s=s+i;
        i=2*i;
        t++;

        if(s>=n)
            break;
    }
    while(s<n)
    {
        s=s+k;
        t++;
    }

    printf("%d",t);
    return 0;
}

    while(s<n)
    {
        s=s+k;
        t++;
    }

Isn't here (n-s)/k iterations?

#pragma optimize( "g", on )