#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
template<class S, class T> inline S min_L(S a,T b){
  return a<=b?a:b;
}
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline void rd(char &c){
  int i;
  for(;;){
    i = my_getchar_unlocked();
    if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF){
      break;
    }
  }
  c = i;
}
inline int rd(char c[]){
  int i;
  int sz = 0;
  for(;;){
    i = my_getchar_unlocked();
    if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF){
      break;
    }
  }
  c[sz++] = i;
  for(;;){
    i = my_getchar_unlocked();
    if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF){
      break;
    }
    c[sz++] = i;
  }
  c[sz]='\0';
  return sz;
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_putchar_unlocked(a);
}
inline void wt_L(int x){
  int s=0;
  int m=0;
  char f[10];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
template<class S, class T> inline S chmin(S &a, T b){
  if(a>b){
    a=b;
  }
  return a;
}
int X;
int Y;
char S[100][102];
int dp1[100][100];
int dp2[100][100];
int main(){
  int i;
  rd(X);
  rd(Y);
  {
    int Lj4PdHRW;
    for(Lj4PdHRW=(0);Lj4PdHRW<(X);Lj4PdHRW++){
      rd(S[Lj4PdHRW]);
    }
  }
  for(i=(0);i<(X);i++){
    int j;
    for(j=(0);j<(Y);j++){
      dp1[i][j] = dp2[i][j] = 1073709056;
    }
  }
  if(S[0][0]=='.'){
    dp1[0][0] = 0;
  }
  else{
    dp2[0][0] = 1;
  }
  for(i=(0);i<(X);i++){
    int j;
    for(j=(0);j<(Y);j++){
      if(i+1 < X){
        if(S[i+1][j] == '.'){
          chmin(dp1[i+1][j], min_L(dp1[i][j], dp2[i][j]));
        }
        else{
          chmin(dp2[i+1][j], min_L(dp1[i][j] + 1, dp2[i][j]));
        }
      }
      if(j+1 < Y){
        if(S[i][j+1] == '.'){
          chmin(dp1[i][j+1], min_L(dp1[i][j], dp2[i][j]));
        }
        else{
          chmin(dp2[i][j+1], min_L(dp1[i][j] + 1, dp2[i][j]));
        }
      }
    }
  }
  int res =min_L(dp1[X-1][Y-1], dp2[X-1][Y-1]);
  wt_L(res);
  wt_L('\n');
  return 0;
}
// cLay varsion 20200321-1

// --- original code ---
// int X, Y;
// char S[100][102];
// 
// int dp1[100][100], dp2[100][100];
// {
//   rd(X,Y,S(X));
//   rep(i,X) rep(j,Y) dp1[i][j] = dp2[i][j] = int_inf;
//   if[S[0][0]=='.', dp1[0][0] = 0, dp2[0][0] = 1];
//   rep(i,X) rep(j,Y){
//     if(i+1 < X){
//       if(S[i+1][j] == '.') dp1[i+1][j] <?= min(dp1[i][j], dp2[i][j]);
//       else                 dp2[i+1][j] <?= min(dp1[i][j] + 1, dp2[i][j]);
//     }
//     if(j+1 < Y){
//       if(S[i][j+1] == '.') dp1[i][j+1] <?= min(dp1[i][j], dp2[i][j]);
//       else                 dp2[i][j+1] <?= min(dp1[i][j] + 1, dp2[i][j]);
//     }
//   }
//   int res = min(dp1[X-1][Y-1], dp2[X-1][Y-1]);
//   wt(res);
// }


Measured memory_bytes: 384