Here my algo:


#include<iostream>
using namespace std;
int main(){
    char c; int i=0;
#ifndef ONLINE_JUDGE
   freopen("input.txt", "rt", stdin);
   freopen("output.txt", "wt", stdout);
#endif
while(cin.get(c)){
if(i==0&&c>='A'&&c<='Z'){cout<<c; i=1;}else{
if(c>='A'&&c<='Z')cout<<char(c-'A'+'a');
else cout<<c;
}
if(c=='.'||c=='!'||c=='?')i=0;
}
return 0; }

Your character count after some trimming is around 225.

My character count is 173:

#include <stdio.h>
int main ()
{
int c,i=1;
while ((c=getchar())!=EOF) {
putchar(i||c<'A'||c>'Z'?c:c-'A'+'a');
i=c>='A'&&c<='Z'?0:strchr(".?!",c)?1:i;
}
return 0;
}