#include<bits/stdc++.h> using namespace std; #define int long long int dp[1000042][3][2]; const int INF = 1e18; signed main() { int N; string sA, sB; cin >> N; cin >> sA >> sB; vector<int> a(N), b(N); for(int i=0; i<N; i++) { a[i] = sA[i]-'0'; b[i] = sB[i]-'0'; } for(int i=0; i<=N; i++) { for(int j=0; j<3; j++) { for(int k=0; k<2; k++) { dp[i][j][k] = INF; } } } dp[0][0][0] = 0; for(int iN = 0; iN < N; iN++) { for(int setPrec = 0; setPrec < 3; setPrec++) { for(int togglePrec = 0; togglePrec < 2; togglePrec++) { for(int setNow = 0; setNow < 3; setNow++) { for(int toggleNow = 0; toggleNow < 2; toggleNow++) { int bit; if(setNow == 0) bit = a[iN]; else bit = setNow-1; if(toggleNow == 1) bit = (bit +1)%2; if(bit == b[iN]) { dp[iN+1][setNow][toggleNow] = min(dp[iN+1][setNow][toggleNow], dp[iN][setPrec][togglePrec] + (setNow!=setPrec && setNow != 0) + (toggleNow > togglePrec)); } } } } } } int ans = INF; for(int setFin = 0; setFin < 3; setFin++) { for(int toggleFin = 0; toggleFin < 2; toggleFin++) { ans = min(ans, dp[N][setFin][toggleFin]); } } printf("%lld\n", ans); }