int N,M;
long S[2] = {0};
char e[1003] = {0};
#define X(x) ((x)&0x1)
#define COLOR(x) ((x)&0x10)

main(){
    scanf("%d%d",&N,&M);
    for (int n = 0; n < N; n++) {
        char ul = 0;
        char l = 0;
        getchar();
        for (int m = 0; m < M; m++) {
            char c = getchar() != '.';
            char u = e[m+1];
            char ur = e[m+2];
            if (!X(c))
                if (!X(u))
                    c = u;
                else if (!X(l))
                    c = l;
                else if (!X(ul))
                    c = ul ^ 0x10;
                else 
                    c = COLOR(l);
            else
                if (!X(u) && !X(l) && !X(ul) && !X(ur))
                    c = COLOR(l) | c;
                else if (X(u))
                    c = u;
                else if (X(l))
                    c = l;
                else if (X(ul))
                    c = ul;
                else
                    c = ur;
            S[!!COLOR(c)] += X(c);
            e[m+1] = c;
            l = c;
            ul = u;
        }
    }
    printf("%ld\n", S[0]>=S[1]?S[0]:S[1]);
}