Stones on the Table

http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=1487

#include <stdio.h>
int main()
{
    int len, cnt;
    char s[55];
    while(scanf("%d%s", &len, s)!=EOF)
    {
        char lastcolor = 0 ;
        cnt = 0 ;
        for(int i=0;i<len;i++)
        {
            if(s[i] != lastcolor)
            {
                cnt++ ;
                lastcolor = s[i] ;
            }
        }
        printf("%d\n", len - cnt) ;
    }
    return 0 ;
}