# rc.py

class RC():
    def __init__(self,nr,nc):
        self.nr=nr; self.nc=nc

    def inc_r(self,ind):
        r,c=self.row_col(ind)
        r+=1
        if r==self.nr: r=0
        if r==(self.nr-1) and c==(self.nc-1): r=0
        return self.indx(r,c)

    def dec_r(self,ind):
        r,c=self.row_col(ind)
        r-=1
        if r<0: r=self.nr-1
        if r==(self.nr-1) and c==(self.nc-1): r=self.nr-2
        return self.indx(r,c)

    def inc_c(self,ind):
        r,c=self.row_col(ind)
        c+=1
        if c==self.nc: c=0
        if r==(self.nr-1) and c==(self.nc-1): c=0
        return self.indx(r,c)

    def dec_c(self,ind):
        r,c=self.row_col(ind)
        c-=1
        if c<0: c=self.nc-1
        if r==(self.nr-1) and c==(self.nc-1): c=self.nc-2
        return self.indx(r,c)

    def row_col(self,ind):
        i=0
        for r in range(self.nr):
            for c in range(self.nc):
                if i==ind: return r,c
                i+=1

    def indx(self,r,c):
        return r*self.nc+c