#include <stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
int n,k;
char a[100002];
scanf("%d %d %s",&n,&k,a);
int countd=0;
int countx=0;
int sum=0;
for(int i=0;i<strlen(a);i++)
{
if(isupper(a[i])) countd++;
else countx++;
}
if(countx>=k) sum+=(countd+k);
else if(countx<k)
{
sum+=(countd+countx-1);
if((k-countx+1)%2!=0) sum++;
}
printf("%d",sum);
}

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