# include<iostream> using namespace std; int main(){ int b,h,n,s,i=0; string a; cin>>h>>s; cin>>a; for(i=0;a[i]!='\0';i++){ if(s>0 and a[i]=='u'){ s--; } if(s<h and a[i]=='d'){ s++; } }cout<<s; return 0; }