#include <algorithm>
#include <string>
#include <iostream>

using namespace std;

#define INF 999999999
#define REP( i , n ) for(__typeof(n) i=0;i!=(n);++i)

typedef pair<char,int> PI;

int length[1000][2], boundary[1000][2], pred[1000][2];

int main()
{
	int N, M;
	cin >> N >> M;
	REP(i,N)
	{
		int x;
		boundary[i][0] = -1;
		REP(j,M)
		{
			cin >> x;
			if(x)
			{
				if(boundary[i][0] == -1)
					boundary[i][0] = j;

				boundary[i][1] = j;
			}
		}
	}

	boundary[N][0] = boundary[N][1] = 0;
	length[N][0] = length[N][1] = 0;

	for(int i = N-1; i >= 0; --i)
	{
		if(boundary[i][0] == -1)
		{
			// prázdný řádek
			length[i][0] = length[i+1][0] + 1;
			length[i][1] = length[i+1][1] + 1;
			boundary[i][0] = boundary[i+1][0];
			boundary[i][1] = boundary[i+1][1];
			pred[i][0] = 0;
			pred[i][1] = 1;
			continue;
		}
		length[i][0] = length[i][1] = INF;
		REP(j,2)
		{
			int x = boundary[i+1][j];
			int d = boundary[i][1] - boundary[i][0];
			int left, right;
			if(x <= boundary[i][0])
			{
				right = boundary[i][1] - x;
				left = right + d;
			}
			else if(x >= boundary[i][1])
			{
				left = x - boundary[i][0];
				right = left + d;
			}
			else
			{
				left = boundary[i][1] - x + d;
				right = x - boundary[i][0] + d;
			}
			left += length[i+1][j] + 1;
			right += length[i+1][j] + 1;
			if(left < length[i][0])
			{
				length[i][0] = left;
				pred[i][0] = j;
			}
			if(right < length[i][1])
			{
				length[i][1] = right;
				pred[i][1] = j;
			}
		}
	}
	int pos, cnt = 0;

	if(length[0][1] < length[0][0])
		pos = 1;
	else
		pos = 0;

	PI path[1000];
	for(int i = 0; i < N; ++i)
	{
		if(i)
			path[cnt++] = PI('U',1);
		int x = boundary[i+1][pred[i][pos]];

		if(x <= boundary[i][0])
		{
			path[cnt++] = PI('R', boundary[i][1] - x);
		}
		else if(x >= boundary[i][1])
		{
			path[cnt++] = PI('L', x - boundary[i][0]);
		}
		else
		{
			int d = boundary[i][1] - boundary[i][0];
			if(!pos)
			{
				path[cnt++] = PI('L', d);
				path[cnt++] = PI('R', boundary[i][1] - x);
			}
			else
			{
				path[cnt++] = PI('R', d);
				path[cnt++] = PI('L', x - boundary[i][0]);
			}
		}
	}
	cout << length[0][pos]-1 << endl;
	while(cnt >= 0)
	{
		REP(i, path[cnt].second)
			cout << path[cnt].first;
		--cnt;
	}
	cout << endl;
	return 0;
}