#include <iostream>

#include<cstring>

#include<algorithm>

using namespace std;

char maze[100][5];

int n,m;

int F=0,I=0,O=0;

int vis[100];

char loc[100][100][5];

int cmp(const void *a,const void *b){

    return strcmp((char*)a,(char*)b);//strcmp()不能直接判断二维数组的大小

}

int check(int cur,int i,int j){//top, right, bottom, and left

    if(i==0&&maze[cur][0]!='F') return 0;

    if(i==n-1&&maze[cur][2]!='F') return 0;

    if(j==0&&maze[cur][3]!='F') return 0;

    if(j==m-1&&maze[cur][1]!='F') return 0;

    if(i>0&&(maze[cur][0]+loc[i-1][j][2]!='I'+'O')) return 0;

    if(j>0&&(maze[cur][3]+loc[i][j-1][1]!='I'+'O')) return 0;

    return 1;

}

int dfs(int x,int y,int cnt){

    if(cnt==n*m){//

        return 1;

    }

    char tmp[5]={0};

    for(int k=0;k<n*m;k++){

        if(!vis[k]&&(strcmp(tmp,maze[k])!=0)&&check(k,x,y)){

                strcpy(tmp,maze[k]);

                strcpy(loc[x][y],maze[k]);

                vis[k]=1;

                if(dfs((cnt+1)/m,(cnt+1)%m,cnt+1)) return 1;

                vis[k]=0;

            }

    }

    return 0;

}

void init(){

    memset(maze,0,sizeof(maze));

    memset(vis,0,sizeof(vis));

    memset(loc,0,sizeof(loc));

    F=0,I=0,O=0;

}

int main(int argc, char** argv) {

    while(scanf("%d %d",&n,&m)!=EOF){

        if(n==0&&m==0) break;

        init();

        for(int i=0;i<n*m;i++){

            scanf("%s",maze[i]);

            for(int j=0;j<4;j++){

                if(maze[i][j]=='F') F++;

                else if(maze[i][j]=='I') I++;

                else if(maze[i][j]=='O') O++;

            }

        }

        if(F!=(m+n)*2||I!=O){

            printf("NO\n");

        }else{

            qsort(maze[0],n*m,sizeof(maze[0]),cmp);//q 

            int Find=dfs(0,0,0);

            if(Find) printf("YES\n");

            else printf("NO\n");

        }

    }

    return 0;

}