int marsExploration(char* s) {
    int change =0 , i , j ;
    char arr[3] = {0} ;
    for (i=0 ;s[i];i+=3)
    {
        if (s[i]=='S')
        {
            arr[0] = 1 ;
        }
        if (s[i+1]=='O')
        {
            arr[1] = 1 ;
        }
        if (s[i+2]=='S')
        {
            arr[2] = 1 ;
        }
        for (j=0;j<3;j++)
        {
            if (arr[j]==0)
            {
                change++;
            }
        }
        for (j=0;j<3;j++)
        {
            arr[j] = 0 ;
        }
    }
    
    return change ;
}