#include using namespace std; #define REP(i,a,n) for(int i=(a); i<(int)(n); i++) #define rep(i,n) REP(i,0,n) #define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it) #define ALLOF(c) (c).begin(), (c).end() typedef long long ll; typedef unsigned long long ull; int main(){ int N, M; cin >> N >> M; string S, T; cin >> S; cin >> T; int SA = 0; int SB = 0; rep(i,S.size()){ if(S[i] == 'A') SA++; else SB++; } int TA = 0; int TB = 0; rep(i,T.size()){ if(T[i] == 'A') TA++; else TB++; } cout << min(SA, SB) + min(TA, TB) << endl; return 0; }