#include<iostream> using namespace std; int main(){ int a,b,i,d; cin>>a>>b; string c; cin>>c; d=c.size(); for(i=0;i<d;i++){ if(b!=0&&c[i]=='u'){ b--; } else if(b!=a&&c[i]=='d') b++; } cout<<b<<endl; return 0; }